add markdown toc stuff

docs/components/progress.md

@@ -5,6 +5,11 @@ title: Progress
 
 Stylize the HTML5 `<progress>` element with a few extra classes and some crafty browser-specific CSS. Be sure to read up on the browser support.
 
+## Contents
+
+* Will be replaced with the ToC, excluding the "Contents" header
+{:toc}
+
 ### Example
 
 {% example html %}