css-unused-selector: Add to message which selector is unused

[dummdidumm]

Is your feature request related to a problem? Please describe.
The css-unused-selector warning message does not contain the name of the unused selector. Adding this would help in scenarios like svelte-check where people do not see the code but only get a list of warnings/errors.

Describe the solution you'd like
Enhancing the message like this: Unused CSS selector ".bla"

Describe alternatives you've considered
Infer the name from start / end, but this does not map back to original code in a good way (if people are using preprocessors like less/scss)

How important is this feature to you?
Nice to have, not super important but I think it's implemented quickly since you already have the start/end position.

Additional context
Related ticket in language-tools: sveltejs/language-tools#434

[Conduitry]

In 3.25.0, the warning message now also tells you what the selector is.