Use SerialAPI polyfill for eScan

[mikaello]

eScan is only available trough the WebUSB interface on OSX (maybe on other OS-s too), and 240/MTR4 is pocky available trough Serial API, this means quite a lot of custom code for each API even if the logic is much the same. It may be possible to use https://github.com/google/web-serial-polyfill directly to simulate Serial API, or a fork of this to implement the same workflow and more code sharing between eScan and the 250/MTR4 implementation.