Unhandled LSP requests declared as capabilities in tilleul

The current implementation of the LanguageServer trait for Tilleul define the capabilities as

ServerCapabilities {
     definition_provider: Some(OneOf::Left(true)),
     text_document_sync: Some(TextDocumentSyncCapability::Kind(TextDocumentSyncKind::FULL)),
     ..ServerCapabilities::default()
}

while tilleul does not currently provide an handle for definition requests or synchronization.