Add a theme changer

[MichaelAgarkov]

Background and motivation

It would be awesome if there would be a function that will change the Control and ControlText variables to make the whole form have different themes, like a dark theme. Maybe also make it match the system settings?

Alternative Designs

• Specify the colours to anything.
• Make a "theme" collection, where forms can have multiple themes to switch through.

Risks

Some programs might use a different variable for the form or text colour, in that case it will stay the same.

Will this feature affect UI controls?

Yes, just a "Theme" selector.