I'm really excited to see this post! I've actually tried doing something similar -- I want to use/create a smartcard reader on the web that works with gpg.
The goal was to port pcsclite or scdaemon to use webusb instead of libusb.
It's been a while; I forget exactly where (very early) I left off/felt defeated. I definitely didn't consider making an additional backend for libusb!
Glad to hear! If you want to give it another try, you should be able to use my linked libusb fork in any app that depends on libusb, and compile that with Emscripten.
The goal was to port pcsclite or scdaemon to use webusb instead of libusb.
It's been a while; I forget exactly where (very early) I left off/felt defeated. I definitely didn't consider making an additional backend for libusb!
Very cool -- I can't wait to see part 2 ;).