This lets web pages access USB devices (with your permission). This has long been supported by Chrome, but Mozilla has not wanted it, at least by default. Fortunately, because add-ons are a thing (for now. make sure to keep fighting for this!), it's possible to change that!
Common reasons for wanting this include programming microcontrollers, 3d-printers, smartphone bootloaders, and similar "physical computing" projects.
In order to make this work, you will need to install a small program on your computer. This is explained in the README. You can then install the .xpi file (on the GitHub Releases page) into your browser (which was _just_ auto-approved while I was typing this announcement up).
Please boost (if you want), test, report bugs, etc. etc. (although do keep in mind that this code is entirely written by a single catgirl)
i think this is the perfect type of project to drop late on a sunday / very early on a monday?