Add the ability to provide a return URL

Add the ability to provide a URL to return to once the form has been completed. No need to provide a user interface in the settings (yet), but simply a query string parameter -- much like SharePoint does it with "Return URL".

Or provide a way to display rich-text/html once the form is completed.

Our desired goal is to be able to link people to forms and return them somewhere or give them a nicer "thank you" message that doesn't look like advertising for Microsoft Forms.