chore(ci): require DevOps review on .github/ (ENG-2017)

This repo accepts pull requests from outside contributors and had no CODEOWNERS
at all, so a workflow change here needed no particular reviewer. Everything
under .github/ decides what runs in CI, on which runner, and with which secrets
in scope, which is a trust boundary rather than product code.

Auto-request only for now. Making it a hard gate needs require_code_owner_reviews
in branch protection, which this repo does not have; that rides ENG-2013's org
ruleset.

Author: lucas-koontz

.github/CODEOWNERS

@@ -0,0 +1,5 @@
+# Everything under .github/ decides what runs in CI, on which runner, and with
+# which secrets in scope. This repo accepts pull requests from outside
+# contributors, so a change here is a change to a trust boundary rather than to
+# the product. DevOps reviews it.
+.github/ @mindsdb/devops