Support for React 18

Hi @rajinwonderland ,

I got this warning when I tried to install this package:

```
react-code-snippet 0.6.13
  └─┬ react-highlight 0.12.0
    ├── ✕ unmet peer react@"^15.0.0 || ^16.0.0": found 18.2.0
    └── ✕ unmet peer react-dom@"^15.0.0 || ^16.0.0": found 18.2.0
```

Is this package compatible with React 18?