allow specification of WebUSB instance to support non-browser environments

[alangecker]

Similar to your (@kdrag0n) webinstaller, I try to develop an more universal installer supporting a wider range of devices and other ROMS like Lineage.

for easier development (and some people would even prefer it) I first did a CLI variant using fastboot.js in node, which didn't work out of the box.

One obstacle is, that this project expects navigator.usb to be present, which makes it difficult to use WebUSB implementation in node like (e.g npm:usb)

Full node support still not given due to following other expectations, which are not handled in this PR:

• Blob required
• crypto required
• ProgressEvent required
• zip.js@2.2.27 doesn't support node

[kdrag0n]

It'd be better to add a FastbootOptions or DeviceOptions object for future-proofing.

{
  webusb: navigator.usb
}

this.usb = options?.webusb ?? navigator.usb