Adding table of contents to docs longer than ~one page.

Change-Id: I3bb3afe88e5c54a3fdbed32a0a0dace1b65e85ee
diff --git a/docs/Testing.md b/docs/Testing.md
index b7b8c93..d79aafc 100644
--- a/docs/Testing.md
+++ b/docs/Testing.md
@@ -1,5 +1,7 @@
 # Testing
 
+[TOC]
+
 ## Overview
 
 Hafnium has 4 main kinds of tests: