Add a test for submitting a form on a modal with the enter key.
Add a test for submitting a form on a modal with the enter key.

This is a basic test for the code introduced in
commit 8477d976890aba5b2659586f663f4aae3472bdf8.

termitnjak/mockup,derFreitag/mockup,derFreitag/mockup,plone/mockup,termitnjak/mockup,domruf/mockup,plone/mockup,domruf/mockup,termitnjak/mockup,termitnjak/mockup,plone/mockup,derFreitag/mockup,derFreitag/mockup,domruf/mockup,domruf/mockup