Docker `release` tag only points to one architecture (amd64)

[pglombardo]

The docker tag command doesn't seem to include both architectures even though both have been pulled and are local. Some searches hints that docker manifest may be the right way but thus far I haven't been able to figure it out.

The release tag is always just a pointer to an existing stable tag such as pglombardo/pwpush-postgres:1.11.1

This tag should contain both architectures.

[dmuhs]

Good catch! Thanks for opening a PR. We appreciate it a lot! 🎉