Add docs cc step to pull request checklist

Author: henrymercer

.github/pull_request_template.md

@@ -7,4 +7,6 @@ Replace this with a description of the changes your pull request makes.
 
 ## Checklist
 
-- [ ] This pull request contains no user-visible changes, or the [CHANGELOG.md](../extensions/ql-vscode/CHANGELOG.md) has been updated.
+- [ ] [CHANGELOG.md](../extensions/ql-vscode/CHANGELOG.md) has been updated to incorporate all user visible changes made by this pull request.
+- [ ] Issues have been created for any UI or other user-facing changes made by this pull request.
+- [ ] `@github/product-docs-dsp` has been cc'd in all issues for UI or other user-facing changes made by this pull request.