I don't know anything about initiating calls from HTML and I don't think there's much value in providing a way to do that by default in the library. That's something that could be implemented via a custom BBCode in an extension or something of the sort.
$configurator->BBCodes->addCustom(
'[tel number={REGEXP=/\+?\d+(?:-\d+)+/;useContent}]{TEXT}[/tel]',
'<a href="tel:{@number}">{TEXT}</a>'
);