Feature Request: Treemaps

## Treemaps
Bar charts and pie charts are some of the most used charts.
- Bar charts arguably provide the best precision out of any chart with humans being able to accurately judge differences in lengths.
- Pie charts can cause problems when trying to compare either many categories or categories with similar sizes.

Treemap charts are an attractive alternative to the over-used bar chart. It can be used in instances where there are many categories and, while not perfect, it mitigates the problems that a pie chart on the similar data could have.

Due to the number of transformations needed to make them, these might be an interesting addition to the Bistro module.

## Info sources
[Treemap](https://plotly.com/python/treemaps/)