Added Black formatting badge

Author: evaherrada

README.rst

@@ -14,6 +14,10 @@ Introduction
     :target: https://github.com/adafruit/Adafruit_CircuitPython_Register/actions/
     :alt: Build Status
 
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 This library provides a variety of data descriptor class for `Adafruit
 CircuitPython <https://github.com/adafruit/circuitpython>`_ that makes it really
 simple to write a device drivers for a I2C and SPI register based devices. Data