Merge bitcoin/bitcoin#29703: doc: Rename contrib/devtools/bitcoin-tidy/README to README.md

669ea0a doc: Rename `contrib/devtools/bitcoin-tidy/README` to `README.md` (Hennadii Stepanov)

Pull request description:

  This PR fixes the file formatting on the GitHub website.

  Before:
  ![image](https://github.com/bitcoin/bitcoin/assets/32963518/e81a61f0-f18c-4917-ae79-d35807e91fa9)

  After:
  ![image](https://github.com/bitcoin/bitcoin/assets/32963518/d2a96317-06d6-4185-b0e8-5e62c75f66b5)

ACKs for top commit:
  maflcko:
    lgtm ACK 669ea0a

Tree-SHA512: 3dfa07a482b5447b6f423946cc463648abbedf1012f2da246b8ce16e6ae3895cdbf956fb2db78735f3e0d88473b9b32f226f2557e0004a0adb69b00f2426a8ca

Author: fanquake