One way to do this is to download the React code (there is button to view the code) and run it locally. You can then run it in a much larger window to get a higher res that you can capture.
The even better way is to integrate the React code as part of your doc site, rather than pre-render it into a png. This way:
It will adapt to the resolution of your users
It will keep its dynamic nature, like showing tooltips as you hover over things
Maybe Dust folks have better guidance.