adding STSPIN

Author: BlitzCityDIY

.gitmodules

@@ -1094,3 +1094,6 @@
 [submodule "libraries/drivers/ina23x"]
 	path = libraries/drivers/ina23x
 	url = https://github.com/adafruit/Adafruit_CircuitPython_INA23x.git
+[submodule "libraries/helpers/stspin"]
+	path = libraries/helpers/stspin
+	url = https://github.com/adafruit/Adafruit_CircuitPython_STSPIN.git

docs/drivers.rst

@@ -101,6 +101,7 @@ Helpers for driving motors, servos, and steppers.
     EMC2101 Fan Controller and Temperature monitor (adafruit_emc2101) <https://docs.circuitpython.org/projects/emc2101/en/latest/>
     MotorKit (adafruit_motorkit) <https://docs.circuitpython.org/projects/motorkit/en/latest/>
     ServoKit (adafruit_servokit) <https://docs.circuitpython.org/projects/servokit/en/latest/>
+    STSPIN Stepper Motor Helper (adafruit_stspin) <https://docs.circuitpython.org/projects/stspin/en/latest/>
 
 Internet of Things Web Service Helpers
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^