[react] [readme] Fix broken documentation links and syntax error in code example - #3304

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: ljharb/require-allow-edits@main. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/