[FEATURE] Symbol references

[SpontanCombust]

Implement "Find References" request and associated with it in the document scope "Document Highlights" request.

https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_references
https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_documentHighlight