Created by: MisatoTremor
The current implementation does not support storing multiple sets of data (the key parameter is mostly useless), which is fixed by this PR.
As a sidenote: The data storage indices for the keys are stored on the element attribute key. HTMLElement does not use this attribute, yet, and to my knowledge no subtype does. But it is a very generic name which might be prone to collide in the future, maybe a more bootstrap specific attribute would be better.