Enable Rust formatter workflow for pull requests

Author: flodolo

.github/workflows/format.yml

@@ -1,9 +1,13 @@
 name: Rustfmt
 
 on:
-  # Triggers the workflow on push request events but only for the master branch
+  # Triggers the workflow on push or pull request events but only for the main branch
   push:
     branches: [ main ]
+  pull_request:
+    branches: [ main ]
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
 
 jobs:
   format: