Is your feature request related to a problem? Please describe.

The built-in styles include nested token styles like this:

https://github.com/conorhastings/react-syntax-highlighter/blob/master/src/styles/prism/ghcolors.js#L163

However as far as I can tell they don't actually seem to work.

Describe the solution you'd like

It would be great if there was some way to target nested tokens like you can when writing a CSS theme for Prism/Highlight.

Describe alternatives you've considered

Tried a bunch of syntaxes to see if anything worked:

<SyntaxHighlighter
  style={{
    '.token.atrule .token.rule': { background: 'pink' }
    'atrule rule': { background: 'pink' }
    'atrule.rule': { background: 'pink' }
  }}
  {/* ... */}
/>