docs: use APP_ prefix instead of reserved GITHUB_ prefix

[joshjohanning]

I saw this PR was merged changing the Client ID and Private Key variable/secret used in the docs.

  client-id: ${{ vars.GITHUB_APP_CLIENT_ID }}
  private-key: ${{ secrets.GITHUB_APP_PRIVATE_KEY }}

However,

Variable name cannot start with "GITHUB_" prefix. (nor can secrets for that matter).  Perhaps just use CLIENT_ID and then use PRIVATE_KEY again.

The same applies for secrets as well.

My PR suggests

  client-id: ${{ vars.APP_CLIENT_ID }}
  private-key: ${{ secrets.APP_PRIVATE_KEY }}

Thanks for the consideration!

[Copilot]

Pull request overview

Updates the README documentation to avoid using the reserved GITHUB_ prefix for GitHub Actions variables/secrets by switching examples to an APP_-prefixed naming scheme.

Changes:

• Replaces GITHUB_APP_CLIENT_ID / GITHUB_APP_PRIVATE_KEY with APP_CLIENT_ID / APP_PRIVATE_KEY in workflow examples.
• Updates the base64 decode example to reference the renamed secret.

Show a summary per file

File	Description
README.md	Adjusts docs examples to avoid reserved GITHUB_-prefixed variable/secret names.

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• Files reviewed: 1/1 changed files
• Comments generated: 1

[Copilot]

Pull request overview

Updates the README workflow examples to avoid using the reserved GITHUB_ prefix for Actions variables/secrets, keeping the docs copy‑pasteable for users configuring client-id and private-key.

Changes:

• Replace vars.GITHUB_APP_CLIENT_ID with vars.APP_CLIENT_ID across usage examples.
• Replace secrets.GITHUB_APP_PRIVATE_KEY with secrets.APP_PRIVATE_KEY across usage examples (including the base64 decode snippet).

Show a summary per file

File	Description
README.md	Updates documentation examples to use non-reserved APP_-prefixed variable/secret names.

Copilot's findings

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• Files reviewed: 1/1 changed files
• Comments generated: 2

[parkerbxyz]

Thank you for catching this and opening this pull request, @joshjohanning! ✨