Add `CODEOWNERS` file with a few examples

[jsmith-bdai]

Description

This PR adds in a CODEOWNERS file so that we can better handle the review request process.

NOTE: This version is not finalized, please add suggestions to other areas on this PR. We can constantly add more as well, I just wanted to get an initial version up and filled in the things I knew off the top of my head :smile:

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes # (issue)

Type of change

• New feature (non-breaking change which adds functionality)

Checklist

• [x] I have run the pre-commit checks with ./isaaclab.sh --format
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• [x] I have added my name to the CONTRIBUTORS.md or my name already exists there