Adding a legend

[ppanko]

I'd like to add a legend to a visual created via render.d3movie. I browsed the documentation, but this does not seem to be a feature.

For example, I would like the visual to include a legend describing the vertex color parameter, including color blocks and appropriate labels for those color blocks, mapped to the vertex color parameter.

Please advise on whether there is a workaround to do this -- thanks!