chore: add .gitattributes, markdownlint config, and about_ help stub

- .gitattributes: mark docs/en-US/* as linguist-generated so platyPS-generated
  help files don't skew GitHub language stats.
- .markdownlint-cli2.jsonc: relax MD013 in tables and code blocks, allow MD024
  duplicate headings under different parents, and ignore AGENTS.md, the
  generated docs/en-US/**, and the instructions/** AI-agent guides.
- docs/en-US/about_{{ModuleName}}.help.md: stub for Get-Help about_<Module>.
  Initialize-Template.ps1 already renames {{ModuleName}} files in docs/en-US.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: tablackburn

.gitattributes

@@ -0,0 +1,2 @@
+# The docs are generated by the build script and should be considered artifacts
+docs/en-US/* linguist-generated

.markdownlint-cli2.jsonc

@@ -0,0 +1,20 @@
+{
+  "$schema": "https://raw.githubusercontent.com/DavidAnson/markdownlint-cli2/v0.19.1/schema/markdownlint-cli2-config-schema.json",
+  "config": {
+    "MD013": {
+      "tables": false,
+      "code_blocks": false
+    },
+    "MD024": {
+      "siblings_only": true
+    }
+  },
+  "ignores": [
+    "AGENTS.md",
+    // Intentionally narrow: only ignores docs/en-US (platyPS-generated help) so that
+    // other markdown files in docs/ are still linted. No other language directories
+    // are expected.
+    "docs/en-US/**",
+    "instructions/**"
+  ]
+}