Sure!

If you want to wrap your head around WebAssembly, we've got a good feature on that over here.

If you want lower-level information about how the rendering pipeline works in Google Docs, a couple of the people who were involved in early versions of the project commented on Hacker News.

If you want to learn more about canvas rendering, how much do you know right now? There are lots of introductory tutorials, but I find it more interesting to see how GoJS (which is much less complex than Docs) creates a higher-level model of shapes, text blocks, and buttons using the canvas. You can drag things around and interact with them, but of course there's no HTML beyond the <canvas> element, which gives you the same idea. Now multiply the complexity by x10 at least!