Add a message explaining the type-feature failure to PR label workflow (#158331)

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Author: StanFromIreland

.github/workflows/require-pr-label.yml

@@ -62,3 +62,6 @@ jobs:
           count: 1
           labels: |
             awaiting merge
+          message: >-
+            This PR is labelled type-feature. All features require approval from a
+            core team member before merge. Found: {{ applied }}