Popper v2 support

[22a]

Popper v2 was officially released a week or two ago. I'm just opening this as a tracking issue to see if/when ember-popper would support it.

[lolmaus]

Yes please!

[alexlafroscia]

In case you're interested in something a little different -- or a path to this addon supporting Popper V2 -- I am working on a modifier-based Ember addon for Popper here:

https://github.com/alexlafroscia/ember-popper-modifier

[pzubar]

Hello! I've decided to try to update the addon's code to support the Popper v2.

Ember-popper is used under the hood of a great ember-attacher package so I thought it would be great to update it afterwards as well (cc @tylerturdenpants).

I am new to ember addons, so I would be glad to see the review comments if possible. What do you think, @kybishop @simonihmig @pzuraq? Thank you in advance!

P. S. I could possibly try to migrate the package code to use https://github.com/floating-ui/floating-ui afterwards that is kinda "Popper v3" (Floating UI is a new Popper name) and seems to be even smaller than Popper v2 🤔

[simonihmig]

I have stopped using this addon a while ago, so I will not be able to do any maintenance/review work here as I did before (to some small extent). Tbh not sure if this addon is still considered actively maintained, and by whom? 🤔