Disable CI runs on non-master pushes.

Author: wRAR

.github/workflows/main.yml

@@ -1,5 +1,9 @@
 name: CI
-on: [push, pull_request]
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
 jobs:
   build:
     runs-on: ubuntu-latest