[clang-tools-extra] [clang-tidy] add modernize-use-constexpr check (PR #146553)

[Julian Schmidt via cfe-commits]

5chmidti wrote:

Sorry for the silly docs mistakes, btw. 

I've updated the docs, added replacement string options, and fixed the `const` keyword removal.

https://github.com/llvm/llvm-project/pull/146553