Merge pull request #368 from kattni/add-adxl37x

Add ADXL37x.

Author: dhalbert

.gitmodules

@@ -872,3 +872,6 @@
 [submodule "libraries/drivers/24lc32"]
 	path = libraries/drivers/24lc32
 	url = https://github.com/adafruit/Adafruit_CircuitPython_24LC32.git
+[submodule "libraries/drivers/adxl37x"]
+	path = libraries/drivers/adxl37x
+	url = https://github.com/adafruit/Adafruit_CircuitPython_ADXL37x.git

docs/drivers.rst

@@ -318,6 +318,7 @@ Motion relating sensing including ``acceleration``, ``magnetic``, ``gyro``, and
 .. toctree::
 
     ADXL34x 3 Axis Accelerometer <https://circuitpython.readthedocs.io/projects/adxl34x/en/latest/>
+    ADXL37x 3 Axis Accelerometer <https://circuitpython.readthedocs.io/projects/adxl37x/en/latest/>
     BNO055 Accelerometer, Magnetometer, Gyroscope and Absolution Orientation <https://circuitpython.readthedocs.io/projects/bno055/en/latest/>
     BNO08X  9 Axis Sensor Fusion IMU <https://circuitpython.readthedocs.io/projects/bno08x/en/latest/>
     BNO08X_RVC Simple UART Heading Library <https://circuitpython.readthedocs.io/projects/bno08x_rvc/en/latest/>