Added Black formatting badge

Author: evaherrada

README.rst

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     :target: https://github.com/adafruit/Adafruit_CircuitPython_ST7565/actions/
     :alt: Build Status
 
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+    :target: https://github.com/psf/black
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 A display control library for ST7565 graphic displays
 
 Dependencies