Add tests for pre-commit container

Run pre-commit on the freshly built container against salt and rc2matrix

.woodpecker/.build.yaml

@@ -1,10 +1,8 @@
-when:
-  path: '*Dockerfile*'
-
 steps:
   build main:
     when:
-      branch: main
+      - event: push
+        branch: main
     image: woodpeckerci/plugin-docker-buildx:4.0.0@sha256:9d24b71c37d7a958d79252e608c4d1a04b02f2e74d4e26003b43e0830038bde0
     pull: true
     settings:
@@ -20,8 +18,9 @@ steps:
 
   build branch:
     when:
-      branch:
+      - event: push
-        exclude: ['main']
+        branch:
+          exclude: ['main']
     image: woodpeckerci/plugin-docker-buildx:4.0.0@sha256:9d24b71c37d7a958d79252e608c4d1a04b02f2e74d4e26003b43e0830038bde0
     pull: true
     settings: