Rename master branch to 'main'

Author: jonkoops

.github/workflows/main.yml

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