Added Black formatting badge

Author: evaherrada

README.rst

@@ -14,6 +14,10 @@ Introduction to Adafruit's PCF8563 Real Time Clock (RTC) Library
     :target: https://github.com/adafruit/Adafruit_CircuitPython_PCF8563/actions/
     :alt: Build Status
 
+.. image:: https://img.shields.io/badge/code%20style-black-000000.svg
+    :target: https://github.com/psf/black
+    :alt: Code Style: Black
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 This is a great battery-backed real time clock (RTC) that allows your
 microcontroller project to keep track of time even if it is reprogrammed,
 or if the power is lost. Perfect for datalogging, clock-building, time