🛠️ Repo: Restore `mocha-github-actions-reporter`

[voxpelli]

Removed mocha-github-actions-reporter because it was being installed within the workflow rather than being a dev dependency of the package.json, which makes versioning of it non-straightforward.

And felt a bit odd to have all the other kinds of reporters provided within the module but not this – if we need it then so do others, we should dogfood it (and possibly offer to upstream it: daniellockyer/mocha-github-actions-reporter#7 (comment))

Originally posted by @voxpelli in #5177 (comment)

[mark-wiemer]

@mostafaNazari702 any desire to help us clean up the comments related to this fix? There are still some todos in mocha.yml referencing this bug, re-opening until those are properly handled :)