✨(react) add a popover component

A design system needs a popover mecanism.
In the select component, this logic is handled by downshift.
We introduce a new component, responsible to open an element in
a popin and close it when the user click outside of it.

packages/react/src/index.scss

@@ -13,6 +13,7 @@
 @import './components/Forms/Switch';
 @import './components/Loader';
 @import './components/Pagination';
+@import './components/Popover';
 
 * {
   font-family: var(--c--theme--font--families--base);