Styling parameters in add_text()

Deck.gl's TextLayer has [many properties](https://github.com/visgl/deck.gl/blob/master/docs/api-reference/layers/text-layer.md) to set the style of the text, including background colour, line height, etc.

It doesn't look like they can be set using mapdeck::add_text(). Is there any other way to set these values? I really need a background behind the text to make it visible.


