Also, Git had it since forever, and since GitHub's diff view isn't particularly convenient for browsing multi-commit PRs you usually review the changes using Git anyway.
That said, I'd ask the contributor to tidy up the branch first. It's kinda disrespecting to ask others to review branches in such state.
> A diff view with reduced white space has been available since 2011 by adding ?w=1 to the URL.
https://github.blog/2018-05-01-ignore-white-space-in-code-re...