Push latest package (docker image) to Github

[tmaier]

Current release is v0.2.126.

However, at https://github.com/superfly/flyctl/pkgs/container/flyctl, I can just see v0.2.72. On https://hub.docker.com/r/flyio/flyctl/tags, I can see v0.2.93.

Both of them are out of date. It would be great to get the latest version as docker image. It would be also great to have this automated on each release.