publish linux/arm64 platform of docker image

[camerondavison]

now that aws has the m6g machines, and apple has the m1 machines that are all arm machines there should be a tag of httpbin with linux/arm64

[arnaudlacour]

while we wait for the MR to go in, you may use the builds from my fork here, which is built for x86_64 and aarch64: https://hub.docker.com/repository/docker/arnaudlacour/httpbin

[Verbunix]

The same issue. Can not use on Mac Apple silicon. Found another service https://github.com/mccutchen/go-httpbin. Simple usage like: docker run -p 8080:8080 mccutchen/go-httpbin