Update Docker build workflow

Added a pull for the previous latest so the layers from those can be reused

.github/workflows/docker.yml

@@ -25,6 +25,10 @@ jobs:
           username: ${{ secrets.DOCKER_USERNAME }}
           password: ${{ secrets.DOCKER_PASSWORD }}
 
+      - name: Pull last image for layer reuse
+        run: |
+          docker pull docker.io/zoraxydocker/zoraxy:latest
+      
       - name: Setup building file structure
         run: |
           cp -lr $GITHUB_WORKSPACE/src/ $GITHUB_WORKSPACE/docker/