message: Add note about testing nRF52840dk
diff: // Libtock regression tests to be used with real hardware.
  -// Requires P0.03 and P0.04 to be connected (on a nRF52 DK).
  +// Requires P0.03 and P0.04 to be connected (on a nRF52 DK) and
  +// P0.01 and P0.03 to be connected (on a nRF52840dk).
  #![no_std]
  extern crate alloc;
  