Allow functions for listbox and defaultListbox props

Extend listbox and defaultListbox prop types to allow functions returning a promise resolving to an array of group settings

src/lib/components/container.jsx

@@ -38,6 +38,7 @@ export default function Container(props) {
     enterKeyHint,
     errorMessage,
     id,
+    listbox,
     listboxIsImmutable,
     maxItems,
     minQueryLength,
@@ -56,11 +57,6 @@ export default function Container(props) {
     Clear
   } = props
 
-  // Destructure listbox prop
-  const listbox = Array.isArray(props.listbox)
-    ? props.listbox
-    : [{ ...props.listbox, ...{ name: '', ratio: maxItems } }]
-
   const listboxId = `${id}-listbox`
   const errorboxId = `${id}-errorbox`