A migration reference for upgrading React codebases to version 19, covering every breaking API change at the source file level. You get a quick lookup table for the common replacements (ReactDOM.render to createRoot, forwardRef as direct props, defaultProps to ES6 defaults) plus links to full before/after code for edge cases. Smart call keeping the PropTypes note, since people still use that package standalone even though React stopped validating it. If you're doing a React 19 upgrade and hitting deprecation warnings, this gives you the exact syntax changes without digging through release notes.
npx skills add https://github.com/github/awesome-copilot --skill react19-source-patterns