Merge #233: chore: add CODEOWNERS file

f326113 chore: add CODEOWNERS file (Luis Schwab)

Pull request description:

  <!-- You can erase any parts of this template not applicable to your Pull Request. -->

  ### Description

  Closes #197.

  Lists ValuedMammal as the owner of `/wallet/`.

  * [X] I've signed all my commits
  * [X] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [X] I ran `cargo fmt` and `cargo clippy` before committing

ACKs for top commit:
  ValuedMammal:
    ACK f326113

Tree-SHA512: 2a5b099be2a7c34c32ef979e059590614b52b0066e8d79c1b138f1e7fcb7b0dc0d71a96fbeb2e3145db890237f6b14cf5e01d7f366d429decff1e7d15e733f66

Author: ValuedMammal

.github/CODEOWNERS

@@ -0,0 +1 @@
+/wallet/ @ValuedMammal