Update main.yml

Author: schnerd

.github/workflows/main.yml

@@ -1,5 +1,7 @@
 name: Validate OpenAPI definition
-on: [push]
+on:
+  pull_request:
+    types: [opened, reopened, synchronize]
 
 jobs:
   test_swagger_editor_validator_service:
@@ -22,4 +24,4 @@ jobs:
         uses: char0n/swagger-editor-validate@v1
         with:
           swagger-editor-url: http://localhost/
-          definition-file: openapi.yaml
+          definition-file: openapi.yaml