Add code search functionality to test plan (#2577)

Author: charisk

docs/test-plan.md

@@ -378,6 +378,7 @@ This requires running a MRVA query and seeing the results view.
 1. Make changes via config file (ensure JSON schema is helping out)
 1. Close and re-open VS Code (ensure lists are there)
 1. Collapse/expand tree nodes
+1. Create a new list, right click and select "Add repositories with GitHub Code Search". Enter the language 'python' and the query "UserMixin". This should show a rate limiting notification after a while but eventually populate the list with roughly 770 items.
 
 Error cases that trigger an error notification: