Makefile improvements

[georgkrause]

I think we should improve the docs Makefile:

• Add a hint that the available commands are run in docker
• Provide a build command to build something we can release

@Sporiff Can you help with the second point?

[Sporiff]

For now we can probably just add a simple build command, since I don't expect we'll be adding translations anytime soon.

[Sporiff]

@georgkrause Is there actually a benefit to using the Makefile to build the site? We're only going to be using GH Actions, so using the Poetry action should work fine for this, shouldn't it?

[georgkrause]

@Sporiff What exactly are you referring to by "Poetry action"?

[Sporiff]

@Sporiff What exactly are you referring to by "Poetry action"?

@georgkrause We have a poetry GitHub action that runs poetry scripts to build things directly. Since we're just going to be running a poetry run sphinx... command anyway, is there are benefit to it being in the Makefile?

[georgkrause]

@Sporiff I think back then we had the plan to build the docs inside of docker, and I don't think this would work with poetry, since it isn't a task runner with all the features. But if this isn't a requirement anymore, we can just drop it.