Add addon compatibility checklist

[lisa-wolfgang]

See https://github.com/ScratchAddons/ScratchAddons/issues/4668#issuecomment-1159514682

This new page specifies which addons need to be considered for each aspect of the website being modified in a given addon.

Todo

• [ ] Complete the checklist with every component of scratch.mit.edu that addons currently affect:
  • [ ] General compatibility
  • [ ] Editor compatibility
    • [ ] Code editor compatibility
    • [ ] Costume editor compatibility
    • [ ] Sound editor compatibility
    • [ ] Other editor compatibility
  • [ ] Project player compatibility
  • [ ] Website compatibility
    • [x] Navbar compatibility
    • [ ] Messages page compatibility
    • [ ] My Stuff page compatibility
    • [ ] Search page compatibility
    • [ ] Project page compatibility
    • [ ] Profile compatibility
    • [ ] Forums compatibility
    • [ ] Other website compatibility
• [ ] Add the following to the point about addon compatibility on the quality guidelines page (pending merge of that PR):

  View the [compatibility checklist](/docs/reference/compatibility-checklist) for common issues to consider.
  

[Hans5958]

You wouldn't need to do the alias. Those are done for old pages that got moved, not new pages.

Also if you wish you can separate it to multiple pages, but I'm not sure the scale of the content would be.