chore: update docker configuration

.github/workflows/docker-image-backend.yml

@@ -0,0 +1,25 @@
+name: Create Docker Image for Backend
+
+on:
+  push:
+    branches: main
+      paths:
+        - 'backend/**'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: checkout code
+        uses: actions/checkout@v2
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+      - name: login to docker registry
+        run: echo "${{ secrets.DOCKER_PASSWORD }}" | docker login -u "${{ secrets.DOCKER_USERNAME }}" --password-stdin
+      - name: build the image
+        run: |
+          docker buildx build --push \
+            --tag stonith404/pingvin-share-backend:latest \
+            --platform linux/amd64,linux/arm64 .