Enable formSubmit component to add a Cancel button.
When clicking the cancel button, the form should be cleared and it should not show validation problems from previous requests anymore.

Original description:
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This is only concerning a single form, not multi-step.

To reproduce the problem:

• in the demo project go to service/contact (author instance)
• add the cancel/back button to the submit part
• enter preview mode
• enter an invalid email address and some text in the message field
• submit the form by clicking "send"

Clicking on the "Cancel" button now should clear the form but it doesn't.
This may be caused by the fact that a "back" button is used instead of a "cancel" button.
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