ci: .github match 'on' from Bitcoin Core

Author: Sjors

.github/workflows/ci.yml

@@ -1,9 +1,13 @@
 name: CI
 on:
+  # See: https://docs.github.com/en/actions/writing-workflows/choosing-when-your-workflow-runs/events-that-trigger-workflows#pull_request.
   pull_request:
+  # See: https://docs.github.com/en/actions/writing-workflows/choosing-when-your-workflow-runs/events-that-trigger-workflows#push.
   push:
-    branches: ['**']
-    tags-ignore: ['**']
+    branches:
+      - '**'
+    tags-ignore:
+      - '**'
 
 concurrency:
   group: ${{ github.event_name != 'pull_request' && github.run_id || github.ref }}