[BUGFIX] Catch submit event while saving shortcut with enter

To save the shortcut with an enter in the input field we need to
catch the submit event and use the same save mechanism as when
using the submit button.

Resolves: #73477
Releases: master,7.6
Change-Id: Icbe78ca2e3082e9eb9aa7a2b70c362d0aaa43934
Reviewed-on: https://review.typo3.org/46726


Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Peter Kraume <peter.kraume@gmx.de>
Tested-by: Peter Kraume <peter.kraume@gmx.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>