Add the tab completion video.

docs/source/user/notebook.rst

@@ -94,7 +94,12 @@ Create a new synchronized view of a cell’s output:
 Tab completion (activated with the ``Tab`` key) now includes additional
 information about the types of the matched items:
 
-.. todo:: Make a screencast video of this?
+.. raw:: html
+
+  <div class="jp-youtube-video">
+     <iframe src="https://www.youtube-nocookie.com/embed/MuNr0i8LgpM?rel=0&amp;showinfo=0" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>
+  </div>
+
 
 The tooltip (activated with ``Shift Tab``) contains additional
 information about objects: