Smaller repo history: remove old yarn files from repo history

[joepio]

The repo size is about 1.5GB, most of which is taken up by old dependencies from .yarn/cache. There are tools that help to remove stuff from git history, but it always mean force-pushing - thus rewriting history. As far as I know there are only 2 contributors right now, so it's a problem we can deal with.

git-filter-repo may be a good pick.

Or https://rtyley.github.io/bfg-repo-cleaner/, but its older.

Also, we might need to delete old publish branches, as these get bigger after every new release.