The markdown generation in ingenious. This will integrate well with static site generators, and the charts are extremely lightweight.

I posted a Show HN a while back for charting project that is also minimal (zero) dependency, in a sense: https://github.com/typpo/quickchart

It's a web service that takes a Chart.js config and renders the chart as an image. Downsides compared to this: not accessible, not as lightweight. Upsides: works in email clients (most of which disable flexbox) and other embedding situations, more customization via Chart.js