After a style dispatch, the middleware hashes the style object and looks up if its already in the cache. If not, add the given classname to the document and add it to the cache:
- Dispatch action to store { type: '...', payload: { ...styles }}
- Hash StyleObject -> '646efd54'
- Check if style is already in cache
- Store renders style to client (or could be anything: server-side to string etc.)
- Return hash