non-modal drawer snap points

[tizu69]

The drawer already supports a non-modal mode where the background stays interactive. (<Drawer modal={false}>)

In some use cases, it may be useful to base this on snap points, to have a drawer that is docked at the bottom but becomes a modal once you swipe it up. Use case here is similar, except you have to tap or swipe down to interact with the background.

(Partially copied from #77)