Stand-alone Dark theme

[zeroeightysix]

I think it would be good to see to have an independent way to enable dark theme without turning it on through OS. Perhaps a similar flag option if ever to be tested.

[#2]

Thank you for this suggestion @zeroeightysix. I will make sure the folks who own themes see it.

[#3]

@zeroeightysix Yes, I agree. Uncoupling it from the OS would be great.