[clang-tools-extra] [clang-tidy][NFC] add '.clang-tidy' config for clang-tidy project (PR #147793)

[via cfe-commits]

EugeneZelenko wrote:

> > How about adding modernize relevant to currently used C++ standard? Also some of readability checks are useful.
> 
> Yes, I will add more and more checks to config. Just started with `bugprone` as it is the most straightforward improvement. Or do you think we can make it in one go?

Yes, one go is straightforward. However, if preliminary code fixes will be necessary, they should go into separate pull request.

https://github.com/llvm/llvm-project/pull/147793