Update CI config

Author: alexcrichton

.github/workflows/main.yml

@@ -1,9 +1,9 @@
 name: CI
 on:
   push:
-    branches: [master]
+    branches: [main]
   pull_request:
-    branches: [master]
+    branches: [main]
 
 jobs:
   test:
@@ -134,4 +134,4 @@ jobs:
           git add .
           git -c user.name='ci' -c user.email='ci' commit -m init
           git push -f -q https://git:${{ secrets.github_token }}@github.com/${{ github.repository }} HEAD:gh-pages
-        if: github.event_name == 'push' && github.event.ref == 'refs/heads/master'
+        if: github.event_name == 'push' && github.event.ref == 'refs/heads/main'