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

[Baranov Victor via cfe-commits]

vbvictor 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.

> Please also consider top-level .clang-tidy file re-formatting.

Noted, will check that.

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