surface.capture().data is not working for iOS

### _Bug report_
**Surface.capture().data** is not working for iOS, returns black pixels [0,0,0,0]. Works fine on Android and Web (DOM).

#### library version
```
├── gl-react@4.0.1
└─┬ gl-react-native@4.0.1
└── gl-react-expo@4.0.1
```

#### Expected behavior
Surface.capture().data should be returning the RGBA value of the specified pixel on Surface

#### Actual behavior
Returns [0, 0, 0, 0] no matter what the colour of the specified pixel

#### Steps to reproduce the behavior
```
const data = this.refs.surface.capture(x, y, 1, 1).data;
console.log("RGBA: ", data);
```
Where **surface** is a reference to the Surface component and **x, y** are the coords of the pixel to return the colour