CONFIG_ZMK_BATTERY_NRF_VDDH and CONFIG_ZMK_BATTERY_VOLTAGE_DIVIDER are
now automatically enabled if a DT node with the matching "compatible"
property is present and enabled, so they no longer need to be manually
set for each board.
* Document the Seeed(uino) XIAO interconnect
* Add metadata files for two upstream boards, XIAO and XIAO BLE.
* Add conf and overlay files to properly configure the boards
for ZMK use.
