Normally in theme.html, you can use
{THEME}
shortocode for the path to the frontend theme folder.
But it doesn't work in plugin shortcodes, so I added the custom shortcode in theme shortcodes.
function sc_theme_path() {
return SITEURL . e_THEME . $this->sitetheme . "/";
}
return SITEURL . e_THEME . $this->sitetheme . "/";
}