Merge #198: chore: add CODEOWNERS file

fa6ccc5 chore: add `CODEOWNERS` file (Luis Schwab)

Pull request description:

  ### Description

  Updated CODEOWNERS file to cover all files in the repo and include both primary and secondary maintainers @oleonardolima and @luisschwab, as per https://github.com/bitcoindevkit#stable.

  ### Checklists

  #### All Submissions:

  * [ ] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `just p` before pushing

ACKs for top commit:
  luisschwab:
    ACK fa6ccc5

Tree-SHA512: 7a043298c1e867b59fafb338de861b6495e6b988474dd15531caa68d4e4be6b6148f0d884a2738af6408bfdb062e922b59e12e14d6ac32ae43732d6200898dc7

Author: luisschwab

.github/CODEOWNERS

@@ -0,0 +1 @@
+* @oleonardolima @luisschwab