fix: eliminate JSX.Element from generated typings

Either add JSDoc or TypeScript annotations so that `Mithril.Children` is always returned in favor of `JSX.Element`.

extensions/statistics/js/src/admin/components/StatisticsWidget.js

@@ -46,6 +46,9 @@ export default class StatisticsWidget extends DashboardWidget {
     return 'StatisticsWidget';
   }
 
+  /**
+   * @return {import('mithril').Children}
+   */
   content() {
     const thisPeriod = this.periods[this.selectedPeriod];