Support for popper VirtualElement as referenceElement and overridable container element

[adri1wald]

Hi,

First of all, I love Mantine, so thanks for building it!

I'd like to be able to supply a virtual element to the <Popper/> component. The usePopper is able to handle virtual elements, making it possible to position the popper relative to the cursor or text selection.

I'd also like to be able to supply a custom container element for the popper's portal.

Edit:
It looks like if I tell <Popper/> that my virtual element is an HTMLElement it "just works"