Merge pull request #227 from relic-se/i2sinout

Add I2SInOut library

.gitmodules

@@ -475,3 +475,6 @@
 [submodule "libraries/drivers/mhz19"]
 	path = libraries/drivers/mhz19
 	url = https://github.com/bablokb/circuitpython-mhz19.git
+[submodule "libraries/helpers/pio_i2s"]
+	path = libraries/helpers/pio_i2s
+	url = https://github.com/relic-se/CircuitPython_PIO_I2S.git

circuitpython_community_library_list.md

@@ -130,6 +130,7 @@ Here is a listing of current CircuitPython Community Libraries. These libraries
 * [CircuitPython PaletteFilter](https://github.com/CedarGroveStudios/CircuitPython_PaletteFilter.git) Replace color index values in a displayio.Palette object \([Docs](https://github.com/CedarGroveStudios/CircuitPython_PaletteFilter/blob/main/media/pseudo_readthedocs_palettefilter.pdf))
 * [CircuitPython PaletteSlice](https://github.com/CedarGroveStudios/CircuitPython_PaletteSlice.git) Wrap a displayio.Palette object to permit list-like slicing \([Docs](https://github.com/CedarGroveStudios/CircuitPython_PaletteSlice/blob/main/media/pseudo_rtd_paletteslice.pdf))
 * [CircuitPython Parse](https://github.com/jimbobbennett/CircuitPython_Parse) Parse (absolute and relative) URLs ([PyPi](https://pypi.org/project/circuitpython-parse)) \([Docs](https://circuitpython.readthedocs.io/projects/parse/en/latest/))
+* [CircuitPython_PIO_I2S](https://github.com/relic-se/CircuitPython_PIO_I2S.git) CircuitPython library to handle bidirectional I2S communication using PIO to be used with audio codecs and microphones \([Docs](https://circuitpython-pio-i2s.readthedocs.io/))
 * [CircuitPython_PunkConsole](https://github.com/CedarGroveStudios/CircuitPython_PunkConsole.git) Emulate the Atari Punk Console \([Docs](https://github.com/CedarGroveStudios/CircuitPython_PunkConsole/blob/main/media/pseudo_readthedocs_cedargrove_punkconsole.pdf))
 * [CircuitPython_RangeSlicer](https://github.com/CedarGroveStudios/CircuitPython_RangeSlicer.git) Scale a range of input values into quantized range using hysteresis for noise reduction \([Docs](https://github.com/CedarGroveStudios/CircuitPython_RangeSlicer/blob/master/media/pseudo_readthedocs_rangeslicer.pdf))
 * [CircuitPython_RGB_SpectrumTools](https://github.com/CedarGroveStudios/CircuitPython_RGB_SpectrumTools.git) Methods and classes for converting a normalized spectral index to RGB color values \([Docs](https://github.com/CedarGroveStudios/CircuitPython_RGB_SpectrumTools/blob/main/media/pseudo_rtd_cedargrove_rgb_spectrumtools.pdf))