only run resume build on update in /markdown

.github/workflows/main.yml

@@ -7,6 +7,8 @@ on:
   # Triggers the workflow on push or pull request events but only for the master branch
   push:
     branches: [ master ]
+    paths:
+      - 'markdown/**'
 
   # Allows you to run this workflow manually from the Actions tab
   workflow_dispatch: