Add trends UI with admin and user settings (#11502)

app/javascript/mastodon/features/getting_started/components/trends.js

@@ -0,0 +1,43 @@
+import React from 'react';
+import ImmutablePureComponent from 'react-immutable-pure-component';
+import PropTypes from 'prop-types';
+import ImmutablePropTypes from 'react-immutable-proptypes';
+import Hashtag from 'mastodon/components/hashtag';
+
+export default class Trends extends ImmutablePureComponent {
+
+  static defaultProps = {
+    loading: false,
+  };
+
+  static propTypes = {
+    trends: ImmutablePropTypes.list,
+    fetchTrends: PropTypes.func.isRequired,
+  };
+
+  componentDidMount () {
+    this.props.fetchTrends();
+    this.refreshInterval = setInterval(() => this.props.fetchTrends(), 36000);
+  }
+
+  componentWillUnmount () {
+    if (this.refreshInterval) {
+      clearInterval(this.refreshInterval);
+    }
+  }
+
+  render () {
+    const { trends } = this.props;
+
+    if (!trends || trends.isEmpty()) {
+      return null;
+    }
+
+    return (
+      <div className='getting-started__trends'>
+        {trends.take(3).map(hashtag => <Hashtag key={hashtag.get('name')} hashtag={hashtag} />)}
+      </div>
+    );
+  }
+
+}