[clang-tools-extra] [clang-tidy][NFC] Add `.editorconfig` for `.rst` files (PR #167269)

[Baranov Victor via cfe-commits]

vbvictor wrote:

> But what about C/C++/Python/CMake files?

For C/C++ we have `clang-format`.
For CMake we have strategy "just make look like everywhere else" so I don't see how we can use different style of Cmake files in `clang-tidy`

https://github.com/llvm/llvm-project/pull/167269