Add check for open API file in CI

Author: curquiza

.github/workflows/validation-file.yml

@@ -0,0 +1,12 @@
+name: Check Open API file
+
+on:
+  pull_request:
+
+jobs:
+  check-open-api-file:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: openapi-validator-action
+      uses: thiyagu06/openapi-validator-action@v1