That is a great question. Hard to say, could be RESTDuino (an idea that was pretty revolutionary at the time it was released, but has become a standard way for web developers to interact with microcontrollers since) or maybe JSFS because it establishes powerful patterns (even if the initial application was pretty simple).

Both are pretty old though so I feel like I should pick something new... 🤔

I publish as much as I can about the things I work on (don't always have time), and open-source everything as well. Github probably has the most (currently migrating to Codeberg) but there's a few posted to hackaday.io as well where you can find some pictures, etc..