message: Add DocumentSymbol[] as return type to onDocumentSymbol. Fixes
diff: import {
  TextDocument, TextDocumentChangeEvent, TextDocumentContentChangeEvent, TextDocumentWillSaveEvent,
  Location, Command, TextEdit, WorkspaceEdit, CompletionItem, CompletionList, Hover,
  - SignatureHelp, Definition, DocumentHighlight, SymbolInformation, WorkspaceSymbolParams, DocumentSymbolParams,
  + SignatureHelp, Definition, DocumentHighlight, SymbolInformation, DocumentSymbol, WorkspaceSymbolParams, DocumentSymbolParams,
  CodeLens, DocumentLink,
  RequestType, RequestType0, RequestHandler, RequestHandler0, GenericRequestHandler, StarRequestHandler,
  NotificationType, NotificationType0, NotificationHandler, NotificationHandler0, GenericNotificationHandler, StarNotificationHandler,
  @@ -1236,7 +1236,7 @@ export interface Connection<PConsole = _, PTracer = _, PTelemetry = _, PClient =
  *
  * @param handler The corresponding handler.
  */
  - onDocumentSymbol(handler: RequestHandler<DocumentSymbolParams, SymbolInformation[] | undefined | null, void>): void;
  + onDocumentSymbol(handler: RequestHandler<DocumentSymbolParams, SymbolInformation[] | DocumentSymbol[] | undefined | null, void>): void;
  /**
  * Installs a handler for the `WorkspaceSymbol` request.
  