microbit vision webapp second step: bluetooth uart
https://github.com/ferryzhou/nezha-ble/tree/main/ble
copied from https://gist.github.com/kotobuki/7c67f8b9361e08930da1a5cfcfb0653f
tested and it works!
https://ferryzhou.github.io/nezha-ble/ble/index.htm