Add ci_success job for stable branch protection (#48)

Adds a ci_success job that depends on all CI matrix jobs completing
successfully. This provides a stable job name for branch protection rules
that won't change when the CI matrix is updated.

Author: jeffreyparker

.github/workflows/php_ci.yml

@@ -34,3 +34,10 @@ jobs:
 
       - name: PHP tests
         run: ./vendor/bin/phpunit
+
+  ci_success:
+    name: CI Success
+    runs-on: ubuntu-latest
+    needs: [ci]
+    steps:
+      - run: echo "All CI jobs passed successfully"