Provide image for arm64 platform

[cfoehrdes]

Problem
The docker image is only published for amd64 architecture. For Developers working on Apple silicon this means they will run in Rosetta2 emulation.

Improvement
Create and push an arm64 build

Alternatives
The current image is working but is running slow due to the emulation. Other alternative is doing a custom build on the development system based on the docker files from the repo.

[neseleznev]

I think the maintainers are waiting for the underlying postgis/postgis image support for the arm64.
You can check the status here: postgis/docker-postgis#216 (comment)
Hopefully, we'll get it soon