Add dark mode to pyreverse

[dgutson]

Current problem

pyreverse output does not fit with dark mode pages

Desired solution

Add an option to set dark mode in pyreverse

Additional context

No response

[dgutson]

CC @qequ

[faisalalisayyed]

i want to work on this issue the below images is made using pyreverse so i have to change the fg and bg to make it dark mode by add like a arg or flag for dark mode if i understand correctly then assign me this issue Thanks..

[Pierre-Sassoulas]

Not sure if changing the background to foreground will make something that actually looks good, but yeah that's the gist of it. There's also multiple outputs (plantuml / dot) to handle.