Add dist/index.js to repository for GitHub Actions distribution

- Updated .gitignore to commit dist/ (required for GitHub Actions to load the action)
- dist/index.js is built from src/index.js using 'npm run build'
- CI/CD workflow includes step to rebuild and verify dist is up to date

Author: oden3000

.gitignore

@@ -4,7 +4,7 @@ node_modules/
 yarn.lock
 
 # Build output
-dist/
+# dist/ is committed to repository for GitHub Actions distribution
 
 # IDE
 .vscode/