docs: add readme

Author: EricCrosson

README.md

@@ -0,0 +1,57 @@
+# install-github-release-binary
+
+**install-github-release-binary** is an opinionated GitHub Action for adding a binary from a GitHub release to your CI `$PATH`.
+
+The primary goals are, in order of priority:
+
+1. control over software supply chain security (SSCS)
+2. execute quickly
+3. avoid rate limits
+
+## Supported releases
+
+## Use
+
+Use this action in a step:
+
+```yaml
+- name: Install flux-capacitor
+  uses: EricCrosson/install-github-release-binary@v1
+  with:
+    repo: EricCrosson/flux-capacitor@v1
+```
+
+## Inputs
+
+| Input Parameter | Required | Description                                                                            |
+| :-------------: | :------: | -------------------------------------------------------------------------------------- |
+|      repo       |   true   | Target repository slug and tag. [[Details](#repo)]                                     |
+|      token      |  false   | GitHub token for REST requests. Defaults to `${{ github.token }}`. [[Details](#token)] |
+
+#### repo
+
+Target repository slug and tag.
+
+Repository slugs are of the format `{owner}/{repository}`.
+For example: `EricCrosson/flux-capacitor`.
+
+Tags are of the format `v{semantic-version}`, where `{semantic-version}` is a [semantic version number].
+Examples:
+
+- `v1`
+- `v1.2`
+- `v1.2.3`
+
+All together, the expected format is `{owner}/{repository}@v{semantic-version}`.
+For example: `EricCrosson/flux-capacitor@v1`.
+
+[semantic version number]: https://semver.org/
+
+#### token
+
+A GitHub token with at least `repo` scope.
+Defaults to the `${{ github.token }}` created automatically by GitHub Actions.
+
+T install a binary from a private GitHub repository, use a [Personal Access Token].
+
+[personal access token]: https://docs.github.com/en/enterprise-server@3.4/authentication/keeping-your-account-and-data-secure/creating-a-personal-access-token

action.yml

@@ -5,7 +5,7 @@ author: Eric Crosson
 
 inputs:
   repo:
-    description: Target GitHub repository
+    description: Target GitHub repository slug and tag
     required: true
   token:
     description: GitHub access token or a Personal Access Token with 'repo' scope