Run workflow on pull request

.github/workflows/main.yml

@@ -1,9 +1,10 @@
-name: build
+name: Dockage CI
 
 on:
   push:
-    branches:
-      - 'master'
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "*" ]
 
 jobs:
   docker: