Add text document sync language server caps

crates/lsp/src/lib.rs

@@ -60,7 +60,16 @@ impl LspBackend {
 impl LanguageServer for LspBackend {
     async fn initialize(&self, _: InitializeParams) -> Result<InitializeResult> {
         Ok(InitializeResult {
-            capabilities: ServerCapabilities::default(),
+            capabilities: ServerCapabilities {
+                text_document_sync: Some(TextDocumentSyncCapability::Options(
+                    TextDocumentSyncOptions {
+                        open_close: Some(true),
+                        change: Some(TextDocumentSyncKind::INCREMENTAL),
+                        ..Default::default()
+                    },
+                )),
+                ..Default::default()
+            },
             server_info: Default::default(),
         })
     }