Build docker image for multiple platforms (#108)

Author: hazim-j

.github/workflows/docker.yml

@@ -21,5 +21,7 @@ jobs:
       - name: Build and push
         uses: docker/build-push-action@v4
         with:
+          context: .
+          platforms: linux/amd64,linux/arm64
           push: true
           tags: stackupwallet/stackup-bundler:latest