Update CODEOWNERS

[dstebila]

Updates Github CODEOWNERS file to reflect more recent active contributors. I've probably missed people, so please make a comment or add to the PR to fix.

Fixes #1843.

• [No] Does this PR change the input/output behaviour of a cryptographic algorithm (i.e., does it change known answer test values)? (If so, a version bump will be required from x.y.z to x.(y+1).0.)
• [No] Does this PR change the list of algorithms available -- either adding, removing, or renaming? Does this PR otherwise change an API? (If so, PRs in fully supported downstream projects dependent on these, i.e., oqs-provider will also need to be ready for review and merge by the time this is merged.)

[dstebila]

Github complains about users in this revised CODEOWNERS file not having write access. We'll have to decide whether to add those people in the TSC config.yaml file or whether to remove them from CODEOWNERS.

[SWilson4]

Github complains about users in this revised CODEOWNERS file not having write access. We'll have to decide whether to add those people in the TSC config.yaml file or whether to remove them from CODEOWNERS.

If we're planning on using the CODEOWNERS file to track code ownership and assign reviews, then I think it makes sense to update config.yaml to add the necessary people to the codeowners team. I will create a draft PR tracking this one in the TSC repo.