Support for mutliple toasters

[rickyzhangca]

First of all much thanks, sonner is beautiful!

This is essential for toasting in dialog/modals, such as your great Vaul

without it, taking Vaul as an example

• with a toaster in root, the toast is dispalyed under the drawer
• right now even if we add another toaster in the drawer, there will be two duplicate toasts, one above drawer and one under

raising z-index does not help because the drawer is outisde of root but toasts are inside

The solution might be similar to timolins/react-hot-toast#383

[emilkowalski]

This is an opinionated library and I don't consider rendering toasts when in a dialog a good pattern so I won't be supporting this. If you really need it, you can always increase the z-index of the toaster.