Add documentation for running clang-format

[sherry-yuan]

Document which clang version to run to avoid workflow failure, clang-format git integration as well installation instruction.

[pcolberg]

Thanks @sherry-yuan, your documentation will make it much easier to pass the clang-format workflow on first try.

[pcolberg]

Thanks @sherry-yuan. I cosmetically revised the Markdown to make it somewhat readable in raw format, but otherwise left everything as is. Good thinking on writing a temporary test of a failing clang-format run 🙂

[pcolberg]

Since I noticed you committed additions with message fixup: You can use git commit --fixup=<commit> to replicate the subject of an earlier commit, preceded by fixup!. When everything is ready for squashing, git rebase -i --autosquash intel/main automatically squashes these commits, discarding their messages.

<commit> can be any "commit-ish", but usually HEAD, HEAD^, etc. is convenient.

[sherry-yuan]

I see, thanks for the tip @pcolberg !