Add Github action for blocking merge without clang format

[samparent97]

No description provided.

[BlakeFreer]

We should use git-clang-format instead of the regular clang-format to avoid formatting otherwise unmodified code. This means that sections of code will not be formatted until an actual modification is performed, but it will maintain our commit history.

See this article for a more detailed explanation https://ortogonal.github.io/cpp/git-clang-format/

Also see #69