docs: Add introductory videos

Signed-off-by: Stewart Smith <stewart@linux.ibm.com>
diff --git a/doc/requirements.txt b/doc/requirements.txt
index b510d7c..0067768 100644
--- a/doc/requirements.txt
+++ b/doc/requirements.txt
@@ -1,3 +1,4 @@
 # Pinned due to https://github.com/sphinx-doc/sphinx/issues/5419
 sphinx==1.7.9
 recommonmark
+sphinxcontrib.youtube