add cache call

.github/workflows/auto_doc.yml

@@ -17,6 +17,9 @@ jobs:
       uses: ammaraskar/sphinx-action@master
       with:
         docs-folder: "doc/"
+        python-version: '3.9'
+        cache: 'pip'
+      run: pip install -r requirements.txt
 
     - name: Upload artifacts
       uses: actions/upload-artifact@v3