[Feature Request] Semantic highlighting for TypeScript/JavaScript

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

This feature was already implemented in vscode, and it's built on top of the same TypeScript compiler that monaco uses, so from what I can tell it should just be possible to port the same code over to monaco-typescript.

I understand the Typescript worker's semantic tokens provider is not the most efficient implementation. I also understand its visual impact when used on top of Monarch will be more disruptive than on top of Textmate, at least for very large files. Yet, the pros clearly outweigh the cons.

If implemented, it could still be marked as experimental and disabled by default. It could also come with a more declarative option for when it should be enabled, e.g max number of characters, and/or max number of lines. The debounce time should also be configurable. When working on small snippets, there's no harm in running it more often.

The Monarch grammars for TS/JS leave a lot to be desired. Semantic highlighting would be a huge step forward.

Start by comparing VS Code's semantic highlighting implementation with the monaco-typescript TypeScript worker, focusing on how semantic tokens are provided over Monarch highlighting. Define the integration and configuration points for experimental, opt-in behavior, character or line limits, and debounce timing. Done means TypeScript and JavaScript semantic highlighting works without being enabled by default.