[Feature request] add option to change ruler colour

[somepaulo]

It's often visually difficult working with the white ruler when developing white backgrounded websites (which most of them are these days). I find it that the dark yellow used by KRuler works best for most circumstances. ScreenRuler allows to customize colours and fonts, which is an excellent option to have.
Any chance you could implement this in some way? Maybe a simple text config file, if not a GUI settings panel?

[epilys]

Looks like this is done in gtk by defining gio setting schemas in xml: https://gtk-rs.org/gtk4-rs/stable/latest/book/settings.html

Will probably use this approach. I would like an XDG_CONFIG_DIR alternative but I don't want to pull an extra dependency just for this.