Add at-symbol prepended to mention span title (#25684)

Co-authored-by: Sam BC <samuel.balbirnie-cumming@xdesign.com>

app/javascript/mastodon/components/status_content.jsx

@@ -104,7 +104,7 @@ class StatusContent extends PureComponent {
 
       if (mention) {
         link.addEventListener('click', this.onMentionClick.bind(this, mention), false);
-        link.setAttribute('title', mention.get('acct'));
+        link.setAttribute('title', `@${mention.get('acct')}`);
         link.setAttribute('href', `/@${mention.get('acct')}`);
       } else if (link.textContent[0] === '#' || (link.previousSibling && link.previousSibling.textContent && link.previousSibling.textContent[link.previousSibling.textContent.length - 1] === '#')) {
         link.addEventListener('click', this.onHashtagClick.bind(this, link.text), false);