Use main branch name in workflows

.github/workflows/android_vulkan.yml

@@ -3,10 +3,10 @@ name: Android (Vulkan)
 on:
   push:
     branches:
-    - master
+    - main
   pull_request:
     branches:
-    - master
+    - main
 
 jobs:
   build:

.github/workflows/ios_metal.yml

@@ -3,10 +3,10 @@ name: iOS (Metal)
 on:
   push:
     branches:
-    - master
+    - main
   pull_request:
     branches:
-    - master
+    - main
 
 jobs:
   build:

.github/workflows/linux_opengl.yml

@@ -3,10 +3,10 @@ name: Linux (OpenGL)
 on:
   push:
     branches:
-    - master
+    - main
   pull_request:
     branches:
-    - master
+    - main
 
 jobs:
   build:

.github/workflows/linux_vulkan.yml

@@ -3,10 +3,10 @@ name: Linux (Vulkan)
 on:
   push:
     branches:
-    - master
+    - main
   pull_request:
     branches:
-    - master
+    - main
 
 jobs:
   build:

.github/workflows/macos_metal.yml

@@ -3,10 +3,10 @@ name: macOS (Metal)
 on:
   push:
     branches:
-    - master
+    - main
   pull_request:
     branches:
-    - master
+    - main
 
 jobs:
   build:

.github/workflows/windows_direct3d11.yml

@@ -3,10 +3,10 @@ name: Windows (Direct3D11)
 on:
   push:
     branches:
-    - master
+    - main
   pull_request:
     branches:
-    - master
+    - main
 
 jobs:
   build:

.github/workflows/windows_direct3d12.yml

@@ -3,10 +3,10 @@ name: Windows (Direct3D12)
 on:
   push:
     branches:
-    - master
+    - main
   pull_request:
     branches:
-    - master
+    - main
 
 jobs:
   build: