only execute build on updates outside /markdown

.github/workflows/docker-update.yml

@@ -10,6 +10,8 @@ on:
   # Triggers the workflow on push events but only for the master branch
   push:
     branches: [ master ]
+    paths-ignore:
+      - 'markdown/**'
 
   # Allows you to run this workflow manually from the Actions tab
   workflow_dispatch: