Add trending links (#16917)

* Add trending links

* Add overriding specific links trendability

* Add link type to preview cards and only trend articles

Change trends review notifications from being sent every 5 minutes to being sent every 2 hours

Change threshold from 5 unique accounts to 15 unique accounts

* Fix tests

app/javascript/mastodon/components/admin/Trends.js

@@ -19,7 +19,7 @@ export default class Trends extends React.PureComponent {
   componentDidMount () {
     const { limit } = this.props;
 
-    api().get('/api/v1/admin/trends', { params: { limit } }).then(res => {
+    api().get('/api/v1/admin/trends/tags', { params: { limit } }).then(res => {
       this.setState({
         loading: false,
         data: res.data,