Add docs path filter to github action

Author: yang-xiaodong

.github/workflows/deploy-to-gh-pages.yml

@@ -4,7 +4,21 @@ on:
     branches:
       - master
 jobs:
+  changes:
+    runs-on: ubuntu-latest
+    outputs:
+      docs: ${{ steps.filter.outputs.docs }}
+    steps:
+    - uses: dorny/paths-filter@v2
+      id: filter
+      with:
+        filters: |
+          docs:
+            - 'docs/**'
+
   build-and-deploy:
+    needs: changes
+    if: ${{ needs.changes.outputs.docs == 'true' }}
     runs-on: ubuntu-latest
     steps:
       - name: Checkout 🛎️