Semantic Tokens support

[Tachi107]

Hi, LSP 3.16 introduced Semantic Tokens, a way to provide nice syntax highlighting.

I'm aware that the vim9 lsp plugin does not currently support this, so I'm opening this issue as a feature request.

Some similar LSP plugins support this feature; it may be helpful to look at how they are implemented:

• NeoVim: https://github.com/neovim/neovim/pull/21100
• vim-lsp: https://github.com/prabirshrestha/vim-lsp/pull/1275