[typescript] folding regions for multi-line comments

[aeschli]

It would if great if typescript would provide folding ranges for

• multiline comments (`/* ... */)
• sequent, full-line, single line comment

see https://github.com/Microsoft/vscode/blob/1cec53cedd4cbab9f528c788b4cd79e9990991f3/extensions/html/server/src/test/folding.test.ts#L178
as an example

[mjbvz]

Opened microsoft/TypeScript#22732 to track this upstream