build(aio): add @usageNotes tag def for API docs (angular#22401)

PR Close angular#22401

Author: petebacondarwin

aio/tools/transforms/angular-api-package/tag-defs/usageNotes.js

@@ -0,0 +1,5 @@
+module.exports = function() {
+  return {
+    name: 'usageNotes'
+  };
+};