Call renderOption with relevant option props

As a client dev
when I custom-render an option
I can have relevant state and props available
so I can render interactive, standards-compliant items in my Dropdown.

---

### When item is a string

```javascript
(

)}
/>
```

### When item is an object

```javascript
(

)}
/>
```

### Applying a class when item is selected

```javascript
(

)}
/>
```

`itemProps` is an object with the following properties

Start at the Dropdown renderOption entry point and inspect how options are currently rendered and what option state is available. Use the string, object, and selected-item examples to verify the intended itemProps contract; done means custom-rendered options receive the relevant props while remaining interactive and standards-compliant.

Written by the indexing model from the issue text.