Adding LIS3MDL

Author: siddacious

.gitmodules

@@ -613,3 +613,6 @@
 [submodule "libraries/drivers/lis2mdl"]
 	path = libraries/drivers/lis2mdl
 	url = https://github.com/adafruit/Adafruit_CircuitPython_LIS2MDL.git
+[submodule "libraries/drivers/lis3mdl"]
+	path = libraries/drivers/lis3mdl
+	url = https://github.com/adafruit/Adafruit_CircuitPython_LIS3MDL.git

docs/drivers.rst

@@ -263,6 +263,7 @@ Motion relating sensing including ``acceleration``, ``magnetic``, ``gyro``, and
     ISM20649 Wide-rage 6-DoF Accelerometer and Gyro <https://circuitpython.readthedocs.io/projects/ism20649/en/latest/>
     L3GD20 3-Axis Gyroscope <https://circuitpython.readthedocs.io/projects/l3gd20/en/latest/>
     LIS2MDL 3-Axis Magnetometer <https://circuitpython.readthedocs.io/projects/lis2mdl/en/latest/>
+    LIS3MDL 3-Axis Magnetometer <https://circuitpython.readthedocs.io/projects/lis3mdl/en/latest/>
     LIS3DH Accelerometer <https://circuitpython.readthedocs.io/projects/lis3dh/en/latest/>
     LSM303 Accelerometer and Magnetometer <https://circuitpython.readthedocs.io/projects/lsm303/en/latest/>
     LSM303 Accelerometer Only<https://circuitpython.readthedocs.io/projects/lsm303-accel/en/latest/>