Fix vendor-prefix console errors (react-native-web)

Hello!

I'm using this library with `react-native-web`, and I'm experiencing several console errors every time I render one of these components. I have included a copy of the errors and stack traces.

- [ ] Warning: Unsupported vendor-prefixed style property mozHyphens. Did you mean MozHyphens? [(Stack trace)](https://github.com/conorhastings/react-native-syntax-highlighter/files/4892758/stack1.txt)
- [ ] Warning: Unsupported vendor-prefixed style property mozTabSize. Did you mean MozTabSize? [(Stack trace)](https://github.com/conorhastings/react-native-syntax-highlighter/files/4892763/stack1.txt)
- [ ] Warning: Unsupported vendor-prefixed style property oTabSize. Did you mean OTabSize? [(Stack trace)](https://github.com/conorhastings/react-native-syntax-highlighter/files/4892765/stack1.txt)
- [ ] Warning: Unsupported vendor-prefixed style property webkitHyphens. Did you mean WebkitHyphens? [(Stack trace)](https://github.com/conorhastings/react-native-syntax-highlighter/files/4892767/stack1.txt)

Here's my implementation:

```jsx
import SyntaxHighlighter from 'react-native-syntax-highlighter`;
import { okaidia } from 'react-syntax-highlighter/dist/styles/prism';

```

Dependencies:

- react@~16.11.0
- react-dom@~16.11.0
- react-native@https://github.com/expo/react-native/archive/sdk-38.0.0.tar.gz
- react-native-web@~0.13.0

Thanks!