Add introduction video link

git-svn-id: https://plugins.svn.wordpress.org/stag-custom-sidebars/trunk@857433 b8457f37-d9ea-0310-8a92-e5e31aec5664
Committing 1.0.6

git-svn-id: https://plugins.svn.wordpress.org/stag-custom-sidebars/trunk@859835 b8457f37-d9ea-0310-8a92-e5e31aec5664