Add basic code to have our own dev guide using mdbook - #3452

Error: failed to remove labels: S-waiting-on-author

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions-ecosystem/action-add-labels@v1, actions-ecosystem/action-remove-labels@v1. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/