Re-add intro to the schedule

Mistook the meaning for an internal TOC (not whether it's included in the schedule).

Author: stephenpcook

_episodes/01_intro.md

@@ -4,7 +4,7 @@ title: Introductions
 order: 1
 session: 1
 length: 10
-toc: false
+toc: true
 adapted: false
 ---