style: add clang-format

[legendecas]

Though the idea might be generally good, I've tested it locally and found that the style change would be around 30k lines size.

[github-actions]

This issue is stale because it has been open many days with no activity. It will be closed soon unless the stale label is removed or a comment is made.

[mhdawson]

I think this can be closed since we've added some support for incrementally checking/updating the format. @legendecas let me know if that is not the case and the issue should still be open.