Allow to add an URL to the implementation manifest

[filip26]

Hi,
just nice to have. Would be great to extend an implementation manifest of url property, beside name, allowing to set an URL pointing to company/product/github page where more information is available. The url property value could be utilized in generated report by turning name into a link.

[davidlehn]

Related: digitalbazaar/mocha-w3c-interop-reporter#26