[folding] Add setting to allow to show first N lines (not 1) of folded block

[4mitch]

During work with XML files I usually want to fold all complex elements of one type. And normally each of them has some ID element at the first-two position inside it.

At the moment I move such ID tags in one line with parent tag - to be able to see it when complex element is folded. But I'd like to have setting which allow me to show first N lines of each folded region.
May be language dependent.

[vscodebot]

(Experimental duplicate detection)
Thanks for submitting this issue. Please also check if it is already covered by an existing one, like:

• [folding] show folding actions at the end of folding range as well (#60670)
• [folding] Move line up/down should skip over folded regions or folded sections (#63972)
• [folding] clicking on on line number of folded line should select full folding range (#59657)
• support easy re-arranging of folded blocks (#49886)
• [folding] show comment first line for folded sections (#31966)

[aeschli]

I think the right approach is if we allow folding providers to define a custom text for the folded line: #70794. That way it can contain a summary that contains tags and id.