Change icons in web UI (#27385)

Co-authored-by: Renaud Chaput <renchap@gmail.com>

app/javascript/mastodon/features/ui/components/column_loading.tsx

@@ -0,0 +1,13 @@
+import Column from '../../../components/column';
+import ColumnHeader from '../../../components/column_header';
+
+interface Props {
+  multiColumn?: boolean;
+}
+
+export const ColumnLoading: React.FC<Props> = (otherProps) => (
+  <Column>
+    <ColumnHeader {...otherProps} />
+    <div className='scrollable' />
+  </Column>
+);