🚧 do not check pushes to non-default branches

.github/workflows/macos.yml

 name: macOS
 
-on: [push, pull_request]
+on:
+  push:
+    branches:
+      - develop
+      - master
+  pull_request:
 
 jobs:
   xcode:

.github/workflows/ubuntu.yml

 name: Ubuntu
 
-on: [push, pull_request]
+on:
+  push:
+    branches:
+      - develop
+      - master
+  pull_request:
 
 jobs:
   ci_test_clang:

.github/workflows/windows.yml

 name: Windows
 
-on: [push, pull_request]
+on:
+  push:
+    branches:
+      - develop
+      - master
+  pull_request:
 
 jobs:
   mingw: