Add stable tag to docker

[Darks1de42]

Is your feature request related to a problem? Please describe.
In the manual stands there is the Tag alpine, but this does not exist.

Describe the solution you'd like
The use of the stable Tag for the latest stable version would be nice. Then you can use an alias which uses always the latest version.

[CMNatic]

Ahh that's interesting. I'll publish the alpine tag. The alias idea for `stable is a good idea. However, there's a problem with the CI/CD pipeline in pushing the actual latest stable release (from the github) to the (dockerhub) repo. This is also on my todo.

Thanks :)