Set environment display to dark mode

Description of the limitation and why it is relevant to address

As a user I want to have the possibility to set the environment to dark mode so that it meets my personal preference.

I think this is relevant for the VIKTOR platform because it allows more freedom and flexibility for the user individually to view their environment.

Submitter proposed design (optional)

None

Current workarounds

None

Requested by

@RamiEvans