Single-select clear event should behave like multi-select clear event

[libklein]

A clear event raised by a multi-select carries a reference to the cleared item in the details field:

https://github.com/rob-balfre/svelte-select/blob/master/src/lib/Select.svelte#L341

The details of clear events raised by single-selects is always undefined:

https://github.com/rob-balfre/svelte-select/blob/master/src/lib/Select.svelte#L468

I think we should align behavior in both cases. Imho, most people would expect a reference to the cleared item in the raised event and there are several usecases:

• Removing the select after it has been cleared
• Adding the removed item to some collection

[rob-balfre]

@libklein thanks very much. Released in 5.1.0