Extension methods to color strings like in npm.colors for JS

[Athari]

Colors module extends string prototype with color properties which generate escape sequences, which creates conscise API for colored console output.

Something like this can be done with CsConsoleFormat. A dirty hacky version can be found in my answer Using colors in console, how to store in a simplified notation, but it doesn't support background colors. Supporting both foreground and background colors would require extension methods for both strings and spans.

Looks like it's a very common use case, so implement this API properly.