[Posted this to the feedback form initially - sorry!]
plotly.js and Google Charts. Would you be interested in adding RGraph (https://www.rgraph.net)? I'm quite
happy to write the article for you if you wish - I could use the Chart.js article as a template.
It's a versatile, free (licensed under MIT license) charts library that I've been developing for over 10
years. It supports a wide range of chart types (including some 3D chart types) and a number of data import
methods (eg CSV, Google Sheets, AJAX, server-side integration documentation). There's lots of documentation
and HOWTO guides on the website.
Here's some links:
Demos of charts: https://www.rgraph.net/demos/index.html
The canvas documentation: https://www.rgraph.net/canvas/index.html
The SVG documentation: https://www.rgraph.net/svg/index.html