 Add a `require_tld` option to `URL` constraint

* New `MISSING_TLD_ERROR` with new UUID value
* New `require_tld : Bool = true` constructor property and `tld_message : String = "This URL does not contain a TLD."`
  * Will release this as a new minor as this is technically breaking
* If `true`, `URI.parse` the value to extract the hostname
  * Add the violation if it does not contain a `.` or is a valid IP address