feat: add GitHub Actions workflow for Docker build and publish

.github/workflows/docker-publish.yml

@@ -0,0 +1,35 @@
+name: Docker Build and Publish
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+
+    steps:
+      # Checkout the repository
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      # Set up Docker Buildx
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
+      # Log in to Docker Hub
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v2
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+
+      # Build and push the multi-platform image
+      - name: Build and push multi-platform Docker image
+        uses: docker/build-push-action@v4
+        with:
+          context: .
+          push: true
+          platforms: linux/amd64,linux/arm64
+          tags: wardy784/caddygen:latest