message: Document that onWillSave handler capabilities reqs
  Fixes
diff: @@ -1115,14 +1115,20 @@ export interface Connection<PConsole = _, PTracer = _, PTelemetry = _, PClient =
  onDidCloseTextDocument(handler: NotificationHandler<DidCloseTextDocumentParams>): void;
  /**
  - * Installs a handler for the `DidSaveTextDocument` notification.
  + * Installs a handler for the `WillSaveTextDocument` notification.
  + *
  + * Note that this notification will not be sent unless your server has the
  + * `textDocumentSync.willSave` capability.
  *
  * @param handler The corresponding handler.
  */
  onWillSaveTextDocument(handler: NotificationHandler<WillSaveTextDocumentParams>): void;
  /**
  - * Installs a handler for the `DidSaveTextDocument` notification.
  + * Installs a handler for the `WillSaveTextDocumentWaitUntil` request.
  + *
  + * Note that this request will not be sent unless your server has the
  + * `textDocumentSync.willSaveWaitUntil` capability.
  *
  * @param handler The corresponding handler.
  */
  