ci(crowd): add CI workflow for Docker image build

Add GitHub Actions CI workflow to build and push Docker
image of Crowd to Docker Hub. Triggered on changes
to the Dockerfile in the main branch.

.github/workflows/docker-publish.yml

@@ -0,0 +1,36 @@
+name: Build and Push Docker Image to Docker Hub
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - Dockerfile
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      # Step 1: Check out the repository containing the code
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      # Step 2: Log in to Docker Hub using the credentials stored in GitHub Secrets
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v2
+        with:
+          username: ${{ secrets.DOCKER_HUB_USERNAME }}
+          password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
+
+      # Step 3: Build the Docker image using the Dockerfile in the repository
+      - name: Build Docker image
+        run: |
+          docker build -t ${{ secrets.DOCKER_HUB_USERNAME }}/crowd:${{ github.sha }} .
+          docker tag ${{ secrets.DOCKER_HUB_USERNAME }}/crowd:${{ github.sha }} ${{ secrets.DOCKER_HUB_USERNAME }}/crowd:6.1.1
+
+      # Step 4: Push the Docker image to Docker Hub
+      - name: Push Docker image to Docker Hub
+        run: |
+          docker buildx create --use
+          docker buildx build --platform linux/amd64,linux/arm64 -t ${{ secrets.DOCKER_HUB_USERNAME }}/crowd:6.1.1 --push .