[codeowners] Add a codeowners file

Author: gregnazario

CODEOWNERS

@@ -0,0 +1,9 @@
+# **Please** keep this file ordered alphabetically by directory paths.
+
+# Owners for the `.github` directory and all its subdirectories.
+
+/.github/ @aptos-labs/developer-platform @aptos-labs/security
+
+# Auto-reviewers for all code
+
+* @aptos-labs/developer-platform @gregnazario