restore release.yml, do multi arch build in docker-build-test.yml

.github/workflows/docker-build-test.yml

@@ -8,14 +8,30 @@ on:
     branches:
       - main
 
+# copy most of these steps from release.yml, but push: false and no tags:
+
 jobs:
   build:
     runs-on: ubuntu-latest
 
     steps:
-    - name: Check out repository
+    - name: Checkout code
       uses: actions/checkout@v3
 
-    - name: Build Docker image
-      run: |
-        docker build -t myapp:latest . -f docker/Dockerfile
+    - name: Set up QEMU
+      uses: docker/setup-qemu-action@v3
+    - name: Set up Docker Buildx
+      uses: docker/setup-buildx-action@v3
+    - name: Login to DockerHub
+      uses: docker/login-action@v3
+      with:
+        username: ${{ secrets.DOCKERHUB_USERNAME }}
+        password: ${{ secrets.DOCKERHUB_PASSWORD }}
+
+    - name: Build and push Docker image
+      uses: docker/build-push-action@v5
+      with:
+        context: .
+        file: ./docker/Dockerfile
+        platforms: linux/amd64,linux/arm64
+        push: false