[Feature Request] Why not provide `getDocumentSymbols` api ?

[xiaoxiyao]

Context

• This issue is not a bug report. (please use a different template for reporting a bug)
• This issue is not a duplicate of an existing issue. (please use the search to find existing issues)

Description

Some relatied issues:
#778
#2959

Monaco Editor Playground Link

No response

Monaco Editor Playground Code

No response

[FrameMuse]

I was just thinking about posting the same request when I found this :)

BTW, there is another related issue #2314