To implement the parent task T419413, that is, add a "reveal password"-button, we need to be able to add a clickable icon to the end of the text-input. Codex already supports this, but we need to add the respective interface to HtmlForm so that the needed html and classes can be added there too.

See the Codex documentation for how this needs to be done: https://doc.wikimedia.org/codex/latest/components/demos/text-input.html#with-icons-1

Acceptance criteria

• it is possible to an icon to the beginning or end of a text input in an HTMLForm field when rendered as codex