Set up qemu and buildx for multiplatform images.

Author: csasarak

.github/workflows/build-docker.yml

@@ -29,6 +29,12 @@ jobs:
             platform: linux/amd64,linux/arm64
 
     steps:
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
       - uses: actions/checkout@v2
 
       - name: Build image