Create bottom sheet with item binding

[4brunu]

This PR fixes #13.

With this PR, it is now possible to show/hide the Botton sheet based on an item being nil or not.

@State var presentedLocation: Location?

.bottomSheet(item: $presentedLocation, height: 700) { place in
   SelectedBusinessSheet(selectedBusiness: place)
}

This is similar to https://developer.apple.com/documentation/swiftui/form/sheet(item:ondismiss:content:)