examples/hwapi: Add config for Zephyr port of 96Boards Carbon.

examples/hwapi/hwconfig_z_96b_carbon.py

+from machine import Signal
+
+# 96Boards Carbon board
+# USR1 - User controlled led, connected to PD2
+# USR2 - User controlled led, connected to PA15
+# BT - Bluetooth indicator, connected to PB5.
+# Note - 96b_carbon uses (at the time of writing) non-standard
+# for Zephyr port device naming convention.
+LED = Signal(("GPIOA", 15), Pin.OUT)