add codeowners

.github/CODEOWNERS

@@ -0,0 +1,14 @@
+# This file contains the code owners for the dbt-common repo.
+# PRs will be require review from the associated
+# team(s) or person(s) that touches any files that are mapped to them.
+#
+# A statement takes precedence over the statements above it so more general
+# assignments are found at the top with specific assignments being lower in
+# the ordering (i.e. catch all assignment should be the first item)
+#
+# Consult GitHub documentation for formatting guidelines:
+# https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners#example-of-a-codeowners-file
+
+# As a default for areas with no assignment,
+# the core team as a whole will be assigned
+*       @dbt-labs/core-team