Only trigger builds on branch main (#389)

Pull requests are already handled otherwise

Author: nipunn1313

.github/workflows/main.yml

@@ -1,7 +1,11 @@
 name: CI
 
 # Run on git push, PR, or manually from the Actions tab
-on: [push, pull_request, workflow_dispatch]
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
 
 jobs:
   run_test: