chore: adding missing examples in the gallery for several chart types (#22597)

superset-frontend/plugins/plugin-chart-handlebars/src/plugin/index.ts

@@ -18,6 +18,8 @@
  */
 import { ChartMetadata, ChartPlugin, t } from '@superset-ui/core';
 import thumbnail from '../images/thumbnail.png';
+import example1 from '../images/example1.jpg';
+import example2 from '../images/example2.jpg';
 import buildQuery from './buildQuery';
 import controlPanel from './controlPanel';
 import transformProps from './transformProps';
@@ -38,6 +40,7 @@ export default class HandlebarsChartPlugin extends ChartPlugin {
       description: t('Write a handlebars template to render the data'),
       name: t('Handlebars'),
       thumbnail,
+      exampleGallery: [{ url: example1 }, { url: example2 }],
     });
 
     super({