Added PyPi installation instructions

Author: evaherrada

README.rst

@@ -33,6 +33,31 @@ Usage Example
 
 See examples/mlx90614_simpletest.py for a demo of the usage.
 
+nstalling 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-mlx90614/>`_. To install for current user:
+
+.. code-block:: shell
+
+    pip3 install adafruit-circuitpython-mlx90614
+
+To install system-wide (this may be required in some cases):
+
+.. code-block:: shell
+
+    sudo pip3 install adafruit-circuitpython-mlx90614
+
+To install in a virtual environment in your current project:
+
+.. code-block:: shell
+
+    mkdir project-name && cd project-name
+    python3 -m venv .env
+    source .env/bin/activate
+    pip3 install adafruit-circuitpython-mlx90614
+
 Contributing
 ============