CI: Lint all Markdown files in the project (#14937)

Adds globs and ignore rules.

This allows as to lint Markdown files locally by running as simple as:

    $ markdownlint-cli2

or automatically fix issues with

   $ markdownlint-cli2 --fix

Author: eksperimental

.github/workflows/ci-markdown.yml

@@ -8,10 +8,10 @@ on:
     branches:
       - "main"
     paths:
-      - "lib/**/*.md"
+      - "**/*.md"
   pull_request:
     paths:
-      - "lib/**/*.md"
+      - "**/*.md"
   workflow_dispatch:
 
 permissions:
@@ -34,7 +34,3 @@ jobs:
 
       - name: Run markdownlint
         uses: DavidAnson/markdownlint-cli2-action@30a0e04f1870d58f8d717450cc6134995f993c63 # v21.0.0
-        with:
-          globs: |
-            lib/elixir/pages/**/*.md
-            README.md

.markdownlint-cli2.jsonc

@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: 2021 The Elixir Team
+{
+  "globs": [
+    "**/*.md"
+  ],
+  "ignores": [
+    ".git/**"
+  ],
+  "gitignore": true,
+  "config": {
+    // Consecutive header levels (h1 -> h2 -> h3).
+    "MD001": false,
+    // Header style. We use #s.
+    "MD003": {
+      "style": "atx"
+    },
+    // Style of unordered lists..
+    "MD007": {
+      "indent": 2,
+      "start_indented": true
+    },
+    // Line length. Who cares.
+    "MD013": false,
+    // This warns if you have "console" or "shell" code blocks with a dollar sign $ that
+    // don't show output. We use those a lot, so this is fine for us.
+    "MD014": false,
+    // Multiple headings with the same content. That's fine.
+    "MD024": false,
+    // Some headers finish with ! because it refers to a function name
+    "MD026": false,
+    // Allow empty line between block quotes. Used by contiguous admonition blocks.
+    "MD028": false,
+    // Allowed HTML inline elements.
+    "MD033": {
+      "allowed_elements": [
+        "h1",
+        "a",
+        "br",
+        "img",
+        "picture",
+        "source",
+        "noscript",
+        "p",
+        "script"
+      ]
+    },
+    // This warns if you have spaces in code blocks. Sometimes, that's fine.
+    "MD038": false,
+    // Code block style. We don't care if it's fenced or indented.
+    "MD046": false,
+    // Our tables are too large to align.
+    "MD060": false
+  }
+}

.markdownlint.jsonc

@@ -6,7 +6,7 @@
 
 # Code of Conduct
 
-Contact: elixir-lang-conduct@googlegroups.com
+Contact: <elixir-lang-conduct@googlegroups.com>
 
 ## Why have a Code of Conduct?
 
@@ -51,15 +51,15 @@ If you participate in or contribute to the Elixir ecosystem in any way, you are
 
 Explicit enforcement of the Code of Conduct applies to the official mediums operated by the Elixir project:
 
-* The [official GitHub projects][1] and code reviews.
-* The official elixir-lang mailing lists.
-* The **[#elixir][2]** IRC channel on [Libera.Chat][3].
+  * The [official GitHub projects][1] and code reviews.
+  * The official elixir-lang mailing lists.
+  * The **[#elixir][2]** IRC channel on [Libera.Chat][3].
 
 Other Elixir activities (such as conferences, meetups, and unofficial forums) are encouraged to adopt this Code of Conduct. Such groups must provide their own contact information.
 
 Project maintainers may block, remove, edit, or reject comments, commits, code, wiki edits, issues, and other contributions that are not aligned to this Code of Conduct.
 
-Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by emailing: elixir-lang-conduct@googlegroups.com. All complaints will be reviewed and investigated and will result in a response that is deemed necessary and appropriate to the circumstances. **All reports will be kept confidential**.
+Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by emailing: <elixir-lang-conduct@googlegroups.com>. All complaints will be reviewed and investigated and will result in a response that is deemed necessary and appropriate to the circumstances. **All reports will be kept confidential**.
 
 **The goal of the Code of Conduct is to resolve conflicts in the most harmonious way possible**. We hope that in most cases issues may be resolved through polite discussion and mutual agreement. Bannings and other forceful measures are to be employed only as a last resort. **Do not** post about the issue publicly or try to rally sentiment against a particular individual or group.
 

CODE_OF_CONDUCT.md

@@ -121,30 +121,30 @@ Please review our [Open Source Policy](OPEN_SOURCE_POLICY.md) for complete
 guidelines on licensing and compliance. Below is a summary of the key points
 affecting **all external contributors**:
 
-- Accepted Licenses: Any code contributed must be licensed under the
+  * Accepted Licenses: Any code contributed must be licensed under the
   `Apache-2.0` license.
-- SPDX License Headers: With the exception of approved test fixture files,
+  * SPDX License Headers: With the exception of approved test fixture files,
   all new or modified files in a pull request must include correct SPDX
   headers. If you are creating a new file under the `Apache-2.0` license, for
   instance, please use:
-    
+
     ```elixir
     # SPDX-License-Identifier: Apache-2.0
     # SPDX-FileCopyrightText: 2021 The Elixir Team
     ```
-    
-- No Executable Binaries: Contributions must **not** include any executable
+
+  * No Executable Binaries: Contributions must **not** include any executable
   binary files. If you require an exception (for example, certain test artifacts),
   please see the policy on how to request approval and document exceptions.
-- Preserving Copyright and License Info: If you copy code from elsewhere,
+  * Preserving Copyright and License Info: If you copy code from elsewhere,
   ensure that **all original copyright and license notices remain intact**. If
   they are missing or incomplete, you must add them.
-- Failure to Comply: Pull requests that do not meet these licensing and
+  * Failure to Comply: Pull requests that do not meet these licensing and
   compliance standards will be rejected or require modifications before merging.
-- Developer Certificate of Origin: All contributions are subject to the
+  * Developer Certificate of Origin: All contributions are subject to the
   Developer Certificate of Origin.
 
-    ```
+    ```text
     By making a contribution to this project, I certify that:
 
     (a) The contribution was created in whole or in part by me and I
@@ -171,7 +171,7 @@ affecting **all external contributors**:
         involved.
     ```
 
-    See http://developercertificate.org/ for a copy of the Developer Certificate
+    See <http://developercertificate.org/> for a copy of the Developer Certificate
     of Origin license.
 
 ## Building documentation

CONTRIBUTING.md

@@ -20,7 +20,7 @@ ensuring that Elixir remains a trusted and innovative open source project.
 ## 2. Scope
 
 This policy applies to the Elixir Programming language, located at
-https://github.com/elixir-lang/elixir. It covers every file, and contribution
+<https://github.com/elixir-lang/elixir>. It covers every file, and contribution
 made, including documentation and any associated assets.
 
 ## 3. Licensing
@@ -29,9 +29,9 @@ All code released by the Elixir team is licensed under the
 [Apache-2.0](./LICENSES/Apache-2.0.txt) license. Additionally, the following
 licenses are recognized as permissible in this project:
 
-- The Unicode license, as documented at
+  - The Unicode license, as documented at
   [LicenseRef-scancode-unicode](./LICENSES/LicenseRef-scancode-unicode.txt)
-- The Elixir Trademark Policy, as documented at
+  - The Elixir Trademark Policy, as documented at
   [LicenseRef-elixir-trademark-policy](./LICENSES/LicenseRef-elixir-trademark-policy.txt)
 
 These licenses are considered acceptable for any files or code that form part of
@@ -161,4 +161,4 @@ necessary, by the EEF CISO. Any significant changes will be communicated to
 contributors and made publicly available.
 
 *Effective Date: 2025-02-20*  
-*Last Reviewed: 2025-11-20*
+*Last Reviewed: 2025-11-20*

OPEN_SOURCE_POLICY.md

@@ -21,7 +21,7 @@ Elixir version | Support
 
 ## Announcements
 
-New releases are announced in the read-only [announcements mailing list](https://groups.google.com/group/elixir-lang-ann). You can subscribe by sending an email to elixir-lang-ann+subscribe@googlegroups.com and replying to the confirmation email. Security notifications [will be tagged with `[security]`](https://groups.google.com/forum/#!searchin/elixir-lang-ann/%5Bsecurity%5D%7Csort:date).
+New releases are announced in the read-only [announcements mailing list](https://groups.google.com/group/elixir-lang-ann). You can subscribe by sending an email to <elixir-lang-ann+subscribe@googlegroups.com> and replying to the confirmation email. Security notifications [will be tagged with `[security]`](https://groups.google.com/forum/#!searchin/elixir-lang-ann/%5Bsecurity%5D%7Csort:date).
 
 You may also see [all releases](https://github.com/elixir-lang/elixir/releases) and [consult all disclosed vulnerabilities](https://github.com/elixir-lang/elixir/security) on GitHub.