Either a Conversation object
(as returned from getOrCreateConversation) or the id field of
a conversation (which you may have stored in your database).
If given the HTML panel called will only show up for that conversation.
Optional, defaults to true. Set false if you don't want the HTML panel to be shown after
createHtmlPanel is called. You can change the visibility of the HTML panels by
calling .hide() or .show() on the HtmlPanel instance returned by createHtmlPanel's promise.
Required. URL you want to load inside the HTML panel.
Url can be absolute ("https://www.example.com/register-form.html") or relative ("register-form.html").
We recommend using same origin pages to have better control of the page.
Learn more about HTML Panels and same origin pages {@link https://talkjs.com/docs/Customizations/HTML_Panels.html | here}.