Include note about RubyMine

doc/development/fe_guide/graphql.md

@@ -777,7 +777,14 @@ Some of our tests load the schema JSON files. To generate these files, run:
 bundle exec rake gitlab:graphql:schema:dump
 ```
 
-You should run this task after pulling from upstream.
+You should run this task after pulling from upstream, or when rebasing your
+branch. This is run automatically as part of `gdk update`.
+
+NOTE:
+If you use the RubyMine IDE, and have marked the `tmp` directory as
+"Excluded", you should "Mark Directory As -> Not Excluded" for
+`gitlab/tmp/tests/graphql`. This will allow the **JS GraphQL** plugin to
+automatically find and index the schema.
 
 #### Mocking response as component data