[clang-tools-extra] Update clang tidy Contributing guide (PR #106672)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> If anyone reads this and tests it out, please tell the results. I'll open a new PR to add the Windows exception if it doesn't work. (Or if there's a better workflow that LLVM uses, do tell.)

Correct, it doesn't work out of the box on Windows.

https://github.com/llvm/llvm-project/pull/106672