Restore main.yml Actions workflow and README badge

[Copilot]

The repository referenced a GitHub Actions badge for .github/workflows/main.yml, but that workflow file was not a valid Actions definition. This updates the workflow target behind the badge so the README points to a real, branch-correct CI workflow again.

• Workflow restoration

  • Replaced the invalid .github/workflows/main.yml contents with a minimal GitHub Actions workflow.
  • Configured the workflow to run on push, pull_request, and manual dispatch for the repository’s primary branch: Main.
  • Kept the job scoped to the repository’s existing validation surface:
    • node --check *.js
    • npm run build

• README badge

  • Added the main.yml workflow badge snippet at the top of README.md so the documented status link resolves to the restored workflow.

• Resulting workflow shape

  name: Main
  
  on:
    push:
      branches: [Main]
    pull_request:
      branches: [Main]
    workflow_dispatch:
  
  jobs:
    validate:
      runs-on: ubuntu-latest
      steps:
        - uses: actions/checkout@v3
        - run: node --check *.js
        - run: npm run build

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