Add baseUrl param for hugo

[Heiss]

Hey,

i saw, that the hugo renderer does not respect the baseUrl. So this PR integrates it in the hugo command. The get_server_url method handles this already, so the baseUrl is in fact a call of this method.

This makes it possible to specify a subdirectory or other hosts ip as localhost (which is now possible because of the latest update with serverURL and serverPort).

[NiklasRosenstein]

Aha, I wasn't aware of that option. Thanks @Heiss! Could I ask you to create/update .changelog/_unreleased.yml per the Contribution guidelines before we merge?

[Heiss]

@NiklasRosenstein done. Hopefully it is correct now. :)

[NiklasRosenstein]

LGTM, thanks! 😃