add a `.git-blame-ignore-revs` file and populate it with a few commits (#45243)
GitHub supports hiding commits from showing up in the diff view (https://docs.github.com/en/repositories/working-with-files/using-files/viewing-a-file\#ignore-commits-in-the-blame-view). This is useful to hide commits that made (automatic) style/whitespace changes that would otherwise clutter up the blame view.