Update events that trigger the Actions workflow

Author: hackebrot

.github/workflows/run-checks.yml

@@ -1,6 +1,16 @@
 name: Run checks
 
-on: [push, pull_request]
+on:
+  push:
+    branches:
+      - main
+    tags:
+      - "[0-9]+.[0-9]+.[0-9]+"
+      - "[0-9]+.[0-9]+.[0-9]+rc[0-9]+"
+
+  pull_request:
+    branches:
+      - main
 
 jobs:
   tox: