Add param to thank-you url submitted to jotform

[kevinhowbrook]

The thank-you url would benefit from being added with a parameter in the jotform side. so the url for the thank you page would be form/thank-you?succes=True or something like that...

This would make it easier to work with analytics and pushing data on successful submissions. Because at the moment any user can request the thank-you page, but with a parameter we could check for that and decide to push js or not

https://github.com/kevinhowbrook/wagtail-jotform/blob/master/wagtail_jotform/wagtail_hooks.py#L10

 thank_you_url = page.full_url + page.specific.reverse_subpage(
            "embedded_form_thank_you"
        )