Added PyPi installation instructions

Author: evaherrada

README.rst

@@ -29,7 +29,8 @@ This is easily achieved by downloading
 `the Adafruit library and driver bundle <https://github.com/adafruit/Adafruit_CircuitPython_Bundle>`_.
 
 Installing from PyPI
---------------------
+====================
+
 On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally `from
 PyPI <https://pypi.org/project/adafruit-circuitpython-pca9685/>`_. To install for current user:
 
@@ -51,7 +52,7 @@ To install in a virtual environment in your current project:
     python3 -m venv .env
     source .env/bin/activate
     pip3 install adafruit-circuitpython-pca9685
-
+    
 Usage Example
 =============