Support `mailto:` scheme in URL class
The URL class currently only supports the http:
and https:
schemes. It would be useful if it also supported the mailto:
scheme since currently if we want to generate this in Kolombido:
<a href="mailto:user@example.com">email address</a>
We need to use:
echo new Kolombido\HTML\Element('a', 'Email', ['href'=>'mailto:user@example.com'])
Which is a tad cumbersome.