CI: Add proper job we can depend on

Author: bastelfreak

.github/workflows/ci.yaml

@@ -50,10 +50,14 @@ jobs:
         run: gem build --strict --verbose *.gemspec
 
   tests:
+    if: always()
     needs:
       - rubocop_and_matrix
       - test
     runs-on: ubuntu-24.04
     name: Test suite
     steps:
-      - run: echo Test suite completed
+      - name: Decide whether the needed jobs succeeded or failed
+        uses: re-actors/alls-green@release/v1
+        with:
+          jobs: ${{ toJSON(needs) }}