Rename JSX files with proper .jsx extension (#23733)

app/javascript/mastodon/components/missing_indicator.jsx

@@ -0,0 +1,29 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import { FormattedMessage } from 'react-intl';
+import illustration from 'mastodon/../images/elephant_ui_disappointed.svg';
+import classNames from 'classnames';
+import { Helmet } from 'react-helmet';
+
+const MissingIndicator = ({ fullPage }) => (
+  <div className={classNames('regeneration-indicator', { 'regeneration-indicator--without-header': fullPage })}>
+    <div className='regeneration-indicator__figure'>
+      <img src={illustration} alt='' />
+    </div>
+
+    <div className='regeneration-indicator__label'>
+      <FormattedMessage id='missing_indicator.label' tagName='strong' defaultMessage='Not found' />
+      <FormattedMessage id='missing_indicator.sublabel' defaultMessage='This resource could not be found' />
+    </div>
+
+    <Helmet>
+      <meta name='robots' content='noindex' />
+    </Helmet>
+  </div>
+);
+
+MissingIndicator.propTypes = {
+  fullPage: PropTypes.bool,
+};
+
+export default MissingIndicator;