Combine darkmode and regular logo

[NotMyFault]

What feature do you want to see added?

Instead of having https://github.com/jenkinsci/design-library-plugin/blob/master/logo-dark.svg and https://github.com/jenkinsci/design-library-plugin/blob/master/logo.svg, we can make use of the prefers-color-scheme: dark attribute to apply colors, based on the theme the user requests.

Such a functionality allows using 1 image for multiple themes, like I did it with the header logo in https://github.com/jenkinsci/jenkins/blob/master/README.md

Upstream changes

No response