[folding] finish language-aware folding

[aeschli]

Finish the work on the HTML and JSON folding providers:

• handle cancellation
• limit the number of ranges transmitted
• support multi-line comments
• stable ranges while editing

Investigate:

• custom folding decorations (...) (for [folding] show comment first line for folded sections #31966)

[DanTup]

@aeschli I noticed this is in the release notes for March but currently only a proposed API - is this planned to ship as a stable API in this release? (If so, will it be moved to vscode.d.ts in advance? dev is simpler when things aren't proposed 😁)

[aeschli]

Yes, this is planned to go to vscode.d.ts once we have enough confidence and reviews.

[DanTup]

@aeschli I'm slightly confused - the top of the release notes say there's language-aware folding, but further down it says the API is proposed. It's unclear whether I can actually implement and ship this yet?

[aeschli]

Language aware folding is now in use by CSS, HTML, JSON, TS, JS, Markdown.
These are the built-in extensions from VSCode. Regular extensions can compile against new proposed APIs, but can not use them in published versions. It would be great if you can try them and give feedback. That gives us the chance to still make modifications.
Once the APIs will become permament in the next release you can also publish your support.

[DanTup]

These are the built-in extensions from VSCode

Ah, didn't realise they could use them, all makes sense now!

I was trying to figure out if I could put them in my release towards the end of the month but I guess it'll need to wait. If I get chance after completing the stuff for this release I'll wire this up on a branch and ensure it all works for us. Thanks!