Update `isWebsite` validation to use a URL parser
Update `isWebsite` validation to use a URL parser

Validating URLs is most correctly done with a URL parser, though regexes
can be made to do the trick sometimes. Rather than making the regex even
gnarlier to read though, I'm proposing here to just use the `URL` class
provided by node and try a parse.

This falls back to the previous regex as some previously-accepted
incomplete URLs (e.g. `host.com/no/scheme/provided`) don't parse as
URLs and it would be undesirable to reject such values if folks have
come to depend on their being accepted.

danielireson/formplug-serverless,danielireson/formplug-serverless