Tweek .github/workflows/ci.yml (update on:, use actions/checkout@v3)

Author: tekezo

Diff for: .github/workflows/ci.yml

@@ -1,13 +1,17 @@
 name: CI
 
-on: [push, pull_request]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
 
 jobs:
   build:
     runs-on: macos-12
 
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v3
         with:
           fetch-depth: 1
       - name: example