[Profile] Make handle button text selectable (#39217)

app/javascript/mastodon/components/account_header/styles.module.scss

@@ -110,6 +110,9 @@
   word-break: break-all;
   text-align: left;
 
+  /* Allow the handle text to be selected */
+  user-select: text;
+
   > svg {
     width: 16px;
     height: 16px;