Element of Margin / Padding accepting invalid values like letters and special chars

MR created with that implemented: https://git.drupalcode.org/project/ebt_core/-/merge_requests/14

Hi RenatoG, thank you! Actually I did it intentionaly to able insert not only px units, but also % and vw, vh, pt. Sometimes it can be useful. But I think it's possible to inherit EBT Settings field widget class and replace it with string, number field type if it will be needed.