There might be wrong usage in the `examples/basic-with-react-hooks`, that will cause the <Alpha/> component not working.

When I try it out the demo using `SketchPicker`, I found out that the `Alpha` handle is not working.

After digging for a while I found the usage from the demo is wrong.

```
// In the demo
const [color, setColor] = useState();
const handleChange = color => setColor(color);
return (

);
```

After adding some logs in the source code(helpers/color.js -> toState()), you can see the `onChange` callback pass a color object to the setColor, which includes a param named `hex`, and that will cause the `toState` function to handle it as a pure hex, so the alpha is lost.

It should be used like this:

```
// In the demo
const [color, setColor] = useState();
const handleChange = color => setColor(color.rgb);
return (

);
```

Start in examples/basic-with-react-hooks and compare its SketchPicker state handling with the callback behavior described in the issue. Read helpers/color.js, especially toState(), then update the demo usage so the Alpha value is preserved and verify that the picker displays transparency correctly.

Written by the indexing model from the issue text.