Merge pull request #247 from FoamyGuy/add_cartesian

adding displayio cartesian

Author: tannewt

.gitmodules

@@ -475,3 +475,6 @@
 [submodule "libraries/drivers/ttp229"]
 	path = libraries/drivers/ttp229
 	url = https://github.com/relic-se/CircuitPython_TTP229.git
+[submodule "libraries/helpers/displayio_cartesian"]
+	path = libraries/helpers/displayio_cartesian
+	url = https://github.com/circuitpython/CircuitPython_Org_DisplayIO_Cartesian.git

circuitpython_community_library_list.md

@@ -124,6 +124,7 @@ Here is a listing of current CircuitPython Community Libraries. These libraries
 * [CircuitPython MorseCode](https://github.com/jposada202020/CircuitPython_MorseCode.git) Circuitpython library to crete Morse code  ([PyPi](https://pypi.org/project/circuitpython-MorseCode)) \([Docs](https://circuitpython-morsecode.readthedocs.io/en/latest/))
 * [CircuitPython Noise](https://github.com/todbot/CircuitPython_Noise.git) ([PyPi](https://pypi.org/project/circuitpython-noise)) \([Docs](https://circuitpython-noise.readthedocs.io/en/latest/)) Simplex (Perlin-like) noise generation
 * [CircuitPython_OhmsLaw](https://github.com/CedarGroveStudios/CircuitPython_OhmsLaw.git) Calculate an Ohm’s Law result from two input parameters \([Docs](https://github.com/CedarGroveStudios/CircuitPython_OhmsLaw/blob/main/media/pseudo_rtd_cedargrove_ohmslaw.pdf))
+* [CircuitPython_Org_DisplayIO_Cartesian](https://github.com/circuitpython/CircuitPython_Org_DisplayIO_Cartesian.git) Graph cartesian widget for displayio ([PyPi](https://pypi.org/project/circuitpython-displayio-cartesian/) \([Docs](https://circuitpython-displayio-cartesian.readthedocs.io/en/latest/))
 * [CircuitPython PaletteFader](https://github.com/CedarGroveStudios/CircuitPython_PaletteFader.git) Color palette and list brightness setter and normalizer tool. \([Docs](https://github.com/CedarGroveStudios/CircuitPython_PaletteFader/blob/main/media/pseudo_rtd_cedargrove_palettefader.pdf))
 * [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))