Drawing "unparented" nodes

[jln-dk]

Hey Adriano
Thank you for creating this library!
As you probably have seen I've created a React wrapper for it. After doing this I have received some requests for drawing "unparented" nodes. So simply just nodes without connections.
Today if you add a node without any connections to it, it won't be rendered. I don't know exactly how they should show on the chart, but maybe just below the rest of it nodes (?).

Any ideas on how to achieve this?

[adrai]

hmmm....
I'm open to extend this, but currently I've 0 time for this.
Feel free to try a PR...