Added usage screencast

Author: captainsafia

README.md

@@ -15,3 +15,6 @@ repository so you can stay on top of the latest updates!
 1. Run `jupyter --config-dir` to determine the location of your Jupyter Notebook configuration
 2. Download `notebook-snippet-manager.js` and `list.js` and copy them to `$(jupyter --config-dir)/nbextensions`.
 3. Run `jupyter nbextension enable notebook-snippet-manager`.
+
+### Usage Screencast
+![Usage Screencast](notebook-snippet-manager-screencast.gif)