tweak initialization docs

README.md

@@ -155,8 +155,11 @@ It's also possible to write presentations using [Markdown](#markdown).
 ### Initialization
 
 If you only have a single presentation on the page we recommend initializing reveal.js using the singleton API.
-```js
-Reveal.initialize({ keyboard: true });
+```html
+<script src="dist/reveal.min.js"></script>
+<script>
+  Reveal.initialize({ keyboard: true });
+</script>
 ```
 
 The `initialize` method returns a promise which will resolve as soon as the presentation is ready and can be interacted with via the API.