Gertty talk: add link to the YouTube video replay

Put link for allowing people to replay the amazing
talk by James Blair about Gertty, the TTY interface to
Gerrit Code Review.

Change-Id: I00bee6820558dc532158908de3ad83b0d56a4f1f
diff --git a/sessions/gertty.md b/sessions/gertty.md
index 2f0da22..13c04de 100644
--- a/sessions/gertty.md
+++ b/sessions/gertty.md
@@ -24,4 +24,6 @@
 This presentation will provide an overview and demonstration of
 Gertty, as well as some discussion about Gerrit's excellent REST API.
 
+[YouTube video replay](https://youtu.be/EP-b5xhH-LY)
+
 *[James E. Blair, Red Hat](../speakers.md#corvus)*