Manim animation engine, for the web.
Changelog | Manim | Suggestions / Improvements | FAQ | Discord Server | Website
Look at the Getting Started section of the website.
You can find a list of examples of animations built with Manim-Web here. Some of them are interactive.
Contributions are always welcome whether it's code, documentation, examples or even improvements to make. You can take a look at the contribution document, there are more details about the whole process. If you want to talk, there is a discord server.