how to embed the complement server into other languages, like ts language

[hans000]

now i have a function like this. i hope i can use language server in other language. just like .html file can write css code.
i want to develop a vscode plugin like styled-components.
but i am not sure wheather it support

type Command = string

function add(value: Command) { ... }

add('say 1') // trigger completion

[SPGoding]

The Spyglass language server itself should work fine other than having some hard dependencies on file systems (most notably for the cache directory and the project root). The difficult part would be trying to integrate it and exchange requests with the TypeScript language service.

[MulverineX]

Prior art: https://github.com/johnsoncodehk/volar (Vue Language Server)
Another example of a benefiting project: https://github.com/TheMrZZ/sandstone (TS commands abstraction. Doesn't include types for NBT, Counts, etc due to performance concerns & TS limitations)

[MulverineX]

A built-in system for modifying other language servers, at least the TSLS, would be valuable. Spyglass Plugins would then use this system for different implementations.