Add a hashtag public link to the trending hashtag page (#17140)

* Add a hashtag public link to the hashtag management page

* Add support for element 'target' to Counter.js.
Remove 'rel' element.

* Update app/javascript/mastodon/components/admin/Counter.js

Co-authored-by: Claire <[email protected]>

Co-authored-by: Eugen Rochko <[email protected]>
Co-authored-by: Claire <[email protected]>

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

@@ -33,6 +33,7 @@ export default class Counter extends React.PureComponent {
     label: PropTypes.string.isRequired,
     href: PropTypes.string,
     params: PropTypes.object,
+    target: PropTypes.string,
   };
 
   state = {
@@ -54,7 +55,7 @@ export default class Counter extends React.PureComponent {
   }
 
   render () {
-    const { label, href } = this.props;
+    const { label, href, target } = this.props;
     const { loading, data } = this.state;
 
     let content;
@@ -100,7 +101,7 @@ export default class Counter extends React.PureComponent {
 
     if (href) {
       return (
-        <a href={href} className='sparkline'>
+        <a href={href} className='sparkline' target={target}>
           {inner}
         </a>
       );