Add CircuitPython_KeyManager library

Author: relic-se

.gitmodules

@@ -463,3 +463,6 @@
 [submodule "libraries/helpers/iperf"]
 	path = libraries/helpers/iperf
 	url = https://github.com/bablokb/circuitpython-iperf.git
+[submodule "libraries/helpers/keymanager"]
+	path = libraries/helpers/keymanager
+	url = https://github.com/relic-se/CircuitPython_KeyManager.git

circuitpython_community_library_list.md

@@ -115,6 +115,7 @@ Here is a listing of current CircuitPython Community Libraries. These libraries
 * [CircuitPython Display_HT16K33](https://github.com/jposada202020/CircuitPython_DISPLAY_HT16K33.git) On display simulation for the HT16K33 driver. Works with 8x8 and 16x8 matrices, as well as 4x7 and 4x14 segments ([PyPi](https://pypi.org/project/circuitpython-display-ht16k33/)) \([Docs](https://circuitpython-display-ht16k33.readthedocs.io/en/latest/))
 * [CircuitPython I2C Button](https://github.com/gmparis/CircuitPython_I2C_Button) CircuitPython I2C Button à la Sparkfun Qwiic Button/Switch/Arcade ([PyPI](https://pypi.org/project/circuitpython-i2c-button/)) \([Docs](https://circuitpython-i2c-button.readthedocs.io/en/latest/))
 * [CircuitPython iperf](https://github.com/bablokb/circuitpython-iperf) CircuitPython port of the iperf3-utility
+* [CircuitPython KeyManager](https://github.com/relic-se/CircuitPython_KeyManager) Helper library to manage notes in musical applications. Includes note priority, arpeggiation, and sequencing. \([Docs](https://circuitpython-keymanager.readthedocs.io/en/latest/))
 * [CircuitPython LeapYear](https://github.com/CedarGroveStudios/CircuitPython_LeapYear.git) Confirms whether a specified year is a leap year \([Docs](https://github.com/CedarGroveStudios/CircuitPython_LeapYear/blob/main/media/pseudo_rtd_cedargrove_leapyear.pdf))
 * [CircuitPython Mag Cal](https://github.com/furbrain/CircuitPython_mag_cal.git) Calibrate magnetic sensors \([Docs](https://circuitpython-mag-cal.readthedocs.io/en/latest/))
 * [CircuitPython MicroOSC](https://github.com/todbot/CircuitPython_MicroOSC.git) ([PyPi](https://pypi.org/project/circuitpython-microosc)) \([Docs](https://circuitpython-microosc.readthedocs.io/en/latest/)) Minimal OSC parser and server for CircuitPython and CPython