chore: add action for format checking

.forgejo/workflows/format_pull.yaml

@@ -1,11 +1,7 @@
-name: Test some stuff
+name: format
 
 on:
-  push:
+  pull_request:
-    branches:
-      - main
-    paths:
-      - .forgejo/workflows/test.yaml
 
 jobs:
   test:
@@ -19,6 +15,4 @@ jobs:
         uses: actions/nix/develop@main
         with:
           flake: .
-          run: |
+          run: treefmt
-            direnv allow
-            treefmt