feat: add cyan accent variant for RareStyle

[alessio-attilio]

Adds a selectable cyan accent variant for the RareStyle theme, applied at runtime by recoloring its purple accent colors.
The variant is exposed as an "Accent color" option in the Interface settings and defaults to the existing purple.

[alessio-attilio]

[loathingKernel]

I cannot describe how bad this way of doing it is. I don't even know where to begin with it.

Make a copy of the theme, change the name, the colors or whatever else you please in the new theme, update any static images, such as the check box checkmarks etc to reflect your preferred color, add the theme to the list of themes, done... this has to be a joke, I cannot imagine why when there is already an example in the code of doing exactly this, the ChildOfMetropolis theme, you would add something completely different. There is a way to do this already and there is an example of it, we do not need a third thing.

The last time you made a similar PR was not merged because the theme was not complete, and because it was touching things outside of itself.

[alessio-attilio]

I liked the idea of creating a variant of RareStyle using cyan. Since I wanted to create a variant that only changed the color, I thought I'd modify the scheme. Can't I just add the ColorScheme?

Also, why are there all these changes in the PR?

[loathingKernel]

Please change the name to something new and unique to it, but other than that, this is exactly how it''s meant to add a new theme, thanks for updating it.

[alessio-attilio]

Do you like "cyanotic"?

[loathingKernel]

It's fine, I guess, I just didn't want it to have Rare in it. The existing style is named like that because it is the default