Styles are missing keys

[svallory]

Original Issue: react-figma#61

I was using createPaintStyle etc. and noticed that styles are missing keys. Would it be possible to add them? I currently extract them manually by substringing the ids. This would also help with react-figma#46

I can contribute them in the future if the team's too busy.

NOTE: react-figma#46 is now #4