Merge bitcoindevkit/bdk#2127: Add CODEOWNERS with primary and secondary maintainers

7eb75c7813bf44b0078f01a5674899273d86cc5d chore: add CODEOWNERS with primary and secondary maintainers (Steve Myers)

Pull request description:

  ### Description

  Add CODEOWNERS file with both primary and secondary maintainers for repo files with overrides for specific sub-crates.  See: https://github.com/bitcoindevkit#stable

  fixes #1926

  ### Notes to the reviewers

  This will trigger a review request for above maintainers for any file changes in the repo.

  see: https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners

  ### Changelog notice

  none

  ### Checklists

  #### All Submissions:

  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)

ACKs for top commit:
  luisschwab:
    ACK 7eb75c7813bf44b0078f01a5674899273d86cc5d
  oleonardolima:
    ACK 7eb75c7813bf44b0078f01a5674899273d86cc5d

Tree-SHA512: 444d7c7376ce30346ae72fb996fd213e831e12615a14dc37094905ce472b786ab7362e4a30609ac50261cbec6d97b1ee6408a34319a1f140d52d93f37a83434a