Comments: "Website" field requires http(s) to work

When using the Jetpack comments form without using a social login, it prompts you for Email address, name and website. If you enter a url without the protocol (like website.com) it will not be accepted, and prompt you to enter a URL. It will only accept it if you add the http or https.

Some users may find this experience a bit confusing, as they would generally not include that without copy/pasting the address directly.

Reported in 651166-zen

Start by reproducing the Jetpack comments form behavior for a non-social-login submission using a website.com value without a protocol. Locate the validation entry point for the Website field and verify that URLs without http or https are accepted while existing valid URLs continue to work.

Written by the indexing model from the issue text.