We did a lot of progress to reduce the bus factor lately, but most of the code is still owned and maintained by me.
I think one way to improve that situation would be to have some reviewers before I merge my contributions, to distribute ownership of the codebase on other people.
If you have some interest in HTML/JS/Python/CSS/Design/Docs, and want to help, do you mind adding your name here so I can ping you when relevant?