Update 'README.md'

README.md

@@ -1,3 +1,7 @@
 # spawn-sticker
 
-A script that let you add stickers on top of HTML elements.
+A script that let you add stickers on top of HTML elements. To make it works just add a `data-sticker` attribute to your element. The content of the sticker will be the value of the attribute.
+
+```html
+<div data-sticker='Hello'>World</div>
+```