fixes #4481 missing LinkHint for YouTube comment textbox

The text input on YouTube is a weird placeholder element when it's not focused yet. That's the reason why the existing LinkHints logic doesn't detect it as clickable. This element can be identified reliably by it's role="textbox" attribute, so this was added to the list of clickableRoles.

Author: philg-dev

content_scripts/link_hints.js

@@ -1144,6 +1144,7 @@ const LocalHints = {
         "menuitemcheckbox",
         "menuitemradio",
         "radio",
+        "textbox",
       ];
       if (role != null && clickableRoles.includes(role.toLowerCase())) {
         isClickable = true;