`EntitiyRef` use a query rather Yoleck entity type name

[idanarye]

Currently it limits itself to a Yoleck entity type:

bevy-yoleck/examples/example3d.rs

Lines 256 to 259 in f26701e

	struct LaserPointer {
	#[yoleck(entity_ref = "Planet")]
	target: YoleckEntityRef,
	}

It would be better to support a query instead, so that any entity that matches the query could be selected.