Add YT video URL to doc (#816)

For a final assignment in a class, I've created a How-To video that showcases how to get setup with API credentials, Redirect URIs, and Spotify Developer Accounts, all of which are necessary prerequisites to using the Spotipy library.

I wanted to do this because, in my past experience, the most frustrating thing about working with APIs and libraries is authentication. Spotipy does a nice job of wrapping some of this and making it easier on the developer, but it still takes some setup before successful use.

Specifically, my video goes through the following:
* Installing Spotipy
* Setting up a Spotify Developer Account
* Configuring the Redirect URI
* Getting the Client Secret and Public Keys
* Setting the envars for use with Spotipy
* Running a sample piece of code from Spotipy to show that things are setup properly

docs/index.rst

@@ -9,7 +9,7 @@ Welcome to Spotipy!
 you get full access to all of the music data provided by the Spotify platform.
 
 Assuming you set the ``SPOTIPY_CLIENT_ID`` and ``SPOTIPY_CLIENT_SECRET``
-environment variables, here's a quick example of using *Spotipy* to list the
+environment variables (here is a `video <https://youtu.be/3RGm4jALukM>`_ explaining how to do so), here's a quick example of using *Spotipy* to list the
 names of all the albums released by the artist 'Birdy'::
 
     import spotipy