Upgrade GitHub workflows; add PR template

[mcmire]

• Test on Nodes 18, 20, and 22 to match the module template
• Add compatibility test
• Update workflows to use action-checkout-and-setup
• Add actionlint step
• Add security code scanner

---

Note

Refactors CI to MetaMask setup, adds Node 22 + compatibility tests, actionlint and security scanning, streamlines release via artifacts, and adds a PR template.

• CI/Workflows:
  • Build/Lint/Test (.github/workflows/build-lint-test.yml):
    • Switch to MetaMask/action-checkout-and-setup@v1 and add Node matrix including 18.x, 20.x, 22.x.
    • Use 22.x for build and lint; expand test to include 22.x.
    • Add compatibility-test job: installs without yarn.lock, runs tests across Node 18/20/22, then restores lockfile.
  • Main (.github/workflows/main.yml):
    • Add check-workflows job with actionlint.
    • Add analyse-code job using reusable security-code-scanner.yml; update needs ordering.
  • Create release PR (.github/workflows/create-release-pr.yml):
    • Replace checkout/setup steps with MetaMask/action-checkout-and-setup@v1 (fetch full history, high-risk); remove explicit Node setup.
  • Publish release (.github/workflows/publish-release.yml):
    • Replace checkout/setup with MetaMask/action-checkout-and-setup@v1.
    • Switch from cache-based flow to build artifacts upload/download between jobs; build once and reuse artifacts for dry-run and publish.
  • Security scanning (.github/workflows/security-code-scanner.yml):
    • New reusable workflow running MetaMask/action-security-code-scanner@v1 with path/rule exclusions and optional metrics/Slack.
• Repo:
  • Add PR template (.github/pull_request_template.md).

^{Written by Cursor Bugbot for commit b4a6697. This will update automatically on new commits. Configure here.}

[github-advanced-security]

This pull request sets up GitHub code scanning for this repository. Once the scans have completed and the checks have passed, the analysis results for this pull request branch will appear on this overview. Once you merge this pull request, the 'Security' tab will show more code scanning analysis results (for example, for the default branch). Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results. For more information about GitHub code scanning, check out the documentation.