First working copy of nrf bootloader that works with Arduino framework.
Advertising name set to SENDANCE_DFU.
Hex file contains bootloader + softdevice.
To download to uC:
nrfjprog -f nrf52 --reset --program debug_feather-express_bootloader-d5b9d97_s140.hex --sectoranduicrerase
Debug version is used for now.