Create CODEOWNERS file

[SWilson4]

Fixes #350.

This is my initial stab at defining CODEOWNERS for the purposes of automatic review requests. It includes

• @baentsch and @ajbozarth for all code, as the people who are most familiar with the project structure.
• @ajbozarth for the CI files.
• @baentsch, @bhess, and @pi-314159 for demos assigned to them in the README.

I haven't included all demos "maintainers" (per the README), only those who currently have write permissions on an OQS repo.

The file is currently invalid because @pi-314159 and @ajbozarth don't have write permissions on the repository. As both have made sizeable contributions to this repo, I propose that we give them write permissions, i.e., elevate them to "codeowner" status for oqs-demos. If there are no objections, I'll create a PR on the tsc repo to add them to the appropriate team.

[SWilson4]

Leaving as draft until the CODEOWNERS file is validated by tsc config.yaml changes.

[baentsch]

This #352 (comment)

I would not personally have the bandwidth the help until March

aligns with the heads-up by @ajbozarth late last year that his focus has changed away from OQS. I thus don't consider it prudent to assign this status to him as there's no guarantee he can spare enough time to thoroughly look at things.

Asking @pi-314159 and @bhess in turn: Can you commit sufficient cycles on short notice to help "shepard through" PRs (check for potential and actual problems, give debugging support to contributors, etc) if auto-tagged "reviewer"? Anyone else in @open-quantum-safe/oqs-committers willing to serve in this role?

(Or ?) Maybe worth while creating a new group "open-quantum-safe/reviewers"? I'd be willing to be a member -- maybe you too, @SWilson4 @praveksharma ?