[css] support quickfix highlights

[aeschli]

Testing #205588

.monaco-editor .lightBulbWidget:after {
    position1: absolute;
    top: 0;
}

Use quickfix on position1. Observe there's no highlighting.

[aeschli]

I assume we need to adopt the feature in the css extension.

This will require adoption in LSP and in the server.

[aeschli]

You can assign the issue to me, unless you plan to add a default implementation of range (in case a provider does not provide a range)

[justschen]

yep, we'd like to leave this for extensions!