Position the main form actions to the bottom of IFrame

Thanks @pivica I turned #11 into a MR. Let's proceed with that.

In a next step we should compare the solution with 📌 Make submit button on modal always visible Needs review and see if it's a duplicate, which one is better and if we should combine them.

thomas.frobieter → made their first commit to this issue’s fork.

Closing this as duplicate of 📌 Make submit button on modal always visible Needs review

PS: The iOS issues should be handled in a separate issue (if they even still exist)