Move donut charts from JS library to simpler SVG

[jancborchardt]

Currently the donut chart display is a quite complicated JS library used for just that one visualization. There’s also some pitfalls like the font being baked-in Arial etc.

What might be nicer is to just do it via SVG:

• https://www.smashingmagazine.com/2015/07/designing-simple-pie-charts-with-css/
• https://medium.com/@heyoka/scratch-made-svg-donut-pie-charts-in-html5-2c587e935d72

Then we would likely also have a much easier time making it look like designed at #36 with the logo worked into it. :)