Add more info to release steps

Author: elenatanasoiu

extensions/ql-vscode/docs/test-plan.md

@@ -9,7 +9,8 @@ effort vs value basis).
 We don't need to test features (and permutations of features) that are covered by automated tests.
 
 ### Before releasing the VS Code extension
-- Check major PRs since the previous release for specific one-off things to test.
+- Check major PRs since the previous release for specific one-off things to test. Based on that, you might want to 
+choose to go through some of the Optional Test Cases.
 - Run a query using the existing version of the extension (to generate an “old” query history item)
 - Go through the required test cases listed below