Add guest accessible chat room

Author: southgate

slides/_posts/bumpers/preroll/0001-01-01-Preroll.md

@@ -10,7 +10,7 @@ diagram_svg_path: "assets/logos/logo-github.svg"
 ---
 
 <h1 contenteditable>Classroom Chat</h1>
-<div class="pseudoLink" contenteditable>githubtraining.campfirenow.com/---</div>
+<div class="pseudoLink" contenteditable>githubtraining.campfirenow.com/73f7a</div>
 
 
 {% capture notes %}