Add theme selection for first run

[CaCTuCaTu4ECKuu]

Tested versions

System information

Not OS related

Issue description

There is a reasons why red theme is suboptimal color scheme for UI and can cause bad UX in the long term
For that reason I suggest to add theme selection at program first run like Visual Studio does

And the other thing...

Full initial setup can be added and include hotkeys selection or some other default configuration selection

Steps to reproduce

N/A

Minimal reproduction project (MRP)

N/A

[Majoramari]

Same idea was in mind, to have a darker gray + this will help with Redot-Engine/redot-engine#688

[SkogiB]

I see no problems with this idea!