message: Updated ChartApi options type assertion
diff: @@ -286,7 +286,7 @@ export class ChartApi implements IChartApi, DataUpdatesConsumer<SeriesType> {
  }
  public options(): Readonly<ChartOptions> {
  - return this._chartWidget.options() as ChartOptions;
  + return this._chartWidget.options() as Readonly<ChartOptions>;
  }
  public takeScreenshot(): HTMLCanvasElement {
  