add fona module

Author: brentru

.gitmodules

@@ -679,3 +679,6 @@
 [submodule "libraries/helpers/ble_berrymed_pulse_oximeter"]
 	path = libraries/helpers/ble_berrymed_pulse_oximeter
 	url = https://github.com/adafruit/Adafruit_CircuitPython_BLE_BerryMed_Pulse_Oximeter.git
+[submodule "libraries/drivers/fona"]
+	path = libraries/drivers/fona
+	url = https://github.com/adafruit/Adafruit_CircuitPython_FONA.git

docs/drivers.rst

@@ -458,3 +458,4 @@ Miscellaneous
     Dymo Scale <https://circuitpython.readthedocs.io/projects/dymoscale/en/latest/>
     Nunchuk <https://circuitpython.readthedocs.io/projects/nunchuk/en/latest/>
     Wiznet5k Ethernet Module <https://circuitpython.readthedocs.io/projects/wiznet5k/en/latest/>
+    FONA Cellular Module <https://circuitpython.readthedocs.io/projects/fona/en/latest/>