Add custom builder image to buildx action

Also added debug to list architectures for buildx. Needless to say,
the buildx action is super flakey (as evidenced by a change to the
README breaking the entire build somehow).

.github/workflows/buildx.yml

@@ -21,6 +21,8 @@ jobs:
             docker login -u "${{ secrets.DOCKER_USERNAME }}" --password-stdin
       - name: build and push the image
         run: |
+          docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
+          docker buildx ls
           docker buildx build --push \
             --tag benbusby/whoogle-search:buildx-experimental \
             --platform linux/amd64,linux/arm/v7,linux/arm64 .