Enforce CI on release branches

.github/workflows/ci_code.yml

@@ -4,6 +4,7 @@ on:
   pull_request:
     branches:
       - main
+      - '[0-9]+.[0-9]+'
     paths: # Paths that may affect code quality
     paths-ignore:
       - ".github/**"
@@ -13,7 +14,6 @@ on:
       - '*.rst'
   workflow_dispatch:
 
-
 concurrency:
   group: ${{ github.ref }}
   cancel-in-progress: true