change markdown code sample syntax

index.html

@@ -138,12 +138,14 @@
 
 						For those of you who like that sort of thing. Instructions and a bit more info available [here](https://github.com/hakimel/reveal.js#markdown).
 
-							<section data-markdown>
-							  ## Markdown support
-
-							  For those of you who like that sort of thing.
-							  Instructions and a bit more info available [here](https://github.com/hakimel/reveal.js#markdown).
-							</section>
+						```
+						<section data-markdown>
+						  ## Markdown support
+
+						  For those of you who like that sort of thing.
+						  Instructions and a bit more info available [here](https://github.com/hakimel/reveal.js#markdown).
+						</section>
+						```
 					</script>
 				</section>