chore: add initial CODEOWNERS

[benkozi]

• Adds initial CODEOWNERS file.
• The chem-core-team must approve merges to develop and main. This required updating the rulesets in settings manually.
• The owners file can be extended to specific code areas as governance develops.
• chem-core-team members can always approve in the absence of an SME, but should generally defer to the individual. Once the SME approves, a core member can quickly follow-up with a review/approval.

Once we like this, we can do the same for CECE.

xref: #193

[benkozi]

Question --> Before going through this, should we rename the "CATChem core team" to "UFS-Chem Core Team"?

[bbakernoaa]

Question --> Before going through this, should we rename the "CATChem core team" to "UFS-Chem Core Team"?

I think just “Chem Core Team” is fine as it rests under UFS-community already :)

[benkozi]

Question --> Before going through this, should we rename the "CATChem core team" to "UFS-Chem Core Team"?

I think just “Chem Core Team” is fine as it rests under UFS-community already :)

Renamed. Thanks @bbakernoaa for making the switch