[Feature request] read key config from eeprom

[biemster]

The ch552 has a guaranteed (per datasheet...) firmware write lifetime of 200 writes. This is quite little, and for experimenters easy to pass in a couple days. If the key config (which characters are send over USB when a key is pressed) could be read from the internal eeprom, at least those experiments would not count to the flash write wear. I'm going to implement this for my macropad (https://hackaday.io/project/189914-rgb-macropad-custom-firmware) so there will be a PR for this at a certain point, but it might take a while due to freetime constraints.