chore: Specify code owners (#1315)

Relates to awslabs/cdk-ops#193

Author: RomainMuller

Diff for: .github/CODEOWNERS

@@ -0,0 +1,12 @@
+# Each line is a file pattern followed by one or more owners (@username or
+# email@address).
+#
+# Order is important. The last matching pattern has the most precedence.
+# So if a pull request only touches javascript files, only these owners
+# will be requested to review.
+#
+# @See https://help.github.com/articles/about-codeowners/
+
+*                               @awslabs/aws-cdk-team
+/docs/                          @Doug-AWS
+/packages/@aws-cdk/aws-code*/   @RomainMuller @skinny85