Add editorOverviewRuler.background colour customisation point

[robertrossmann]

Allow themes to customise the editor overview ruler's background colour. 🎨 This PR adds a new theme variable, editorOverviewRuler.background. The background colour is used in only certain circumstances:

• a theme or user must provide a value for this colour contribution (obviously 😄)
• the minimap must be enabled and must be placed on the right side of the editor to have this background colour, otherwise the ruler's background is transparent

You can see the background colour in action in the screenshots below.

Motivation

In my theme, Remedy, I try to follow a simple rule - code gets its background colour and everything else (UI elements) get a different colour to distinguish UI from "codable area". The overview ruler did not fit into that scheme.

Screenshots

Before this PR / no colour configured for editorOverviewRuler.background

After this PR and a colour provided for editorOverviewRuler.background

Minimap is on left side of the editor -> no background colour used

Minimap is disabled -> no background colour used

Diff views do not have a minimap -> no background colour used

[robertrossmann]

I just rebased this on top of current master. Is there anything I can do to get this merged in? 🙏 ❤️ @aeschli

Thanks in advance!

[aeschli]

Change and color name looks good to me. @alexdima Any concerns?

[robertrossmann]

Any hopes of getting this in before the endgame freeze? 🙏 I would love to see this in 1.45 release. ❤️ Thanks a lot!

[alexdima]

LGTM, thank you!

[robertrossmann]

Yay, thanks for getting this in for the April release! ❤️🚀

[nazartt8]

Hi robertrossmann, I use VS Code in my Windows-10. I like its color theme "Tomorrow Light Blue". And have successfully changed some colors of this theme(e.g. color for comment, color for selection-highlight etc) by modifying content of a file named "tomorrow-night-blue-theme.json". But one COLOR I've been trying so hard just couldn't manage to change it. That is color of "searching result", the color is insignificant that makes located results hardly to be differentiated. Hope you can assist. Thank you!

[robertrossmann]

@nazartt8 I think you should not modify the theme file directly, instead, change the colours in your settings:

https://vscode.readthedocs.io/en/latest/getstarted/theme-color-reference

[nazartt8]

@robertrossmann Thanks so much. You've saved my time. And I've learned new thing. It works now. Appreciated!