idea: use semantic tokens with rich informations from the compiler

[adelaett]

using semantics tokens, it is possible to indicate part of a document (for exemple a variable name) using information gathered by the LSP. Here is what i found on the implementation of this kind of feature : https://github.com/microsoft/vscode-extension-samples/tree/main/semantic-tokens-sample.

This could be used by the catala-language server to highlight variables based on their type.