Refactor data.js to use a `Map`

It seems dom/data.js is the perfect candidate for using a Map instead of the custom implementation.

[Johann-S]

yep it’s intended currently we don’t allow to use more than one plugin on a element

[alpadev]

@Johann-S sorry my stupid questions, but I try to fully understand the intention behind this code.

The current implementation, as far as I get it, doesn’t allow for multiple data on a single element at the same time, because setData will reuse the bsKey if it exists and override whatever data that is in storeData (without updating the key in that case). If you call setData on an element with different keys it will always override the information of the first used key, and getData will always return null for every other key aside the first one used. That’s the intended design?

Here is an example of an albeit fictional case that shows the implication of what I’m trying to say: https://codepen.io/-alpa-/pen/KKMExwM