Merge pull request #555 from Jason-Cooke/patch-2

docs: fix typo

README.md

@@ -108,7 +108,7 @@ all the crazy ideas related to AR.js.
 - How to write a AR.js application ?
 Here is a [full tutorial](https://marmelab.com/blog/2017/06/19/augmented-reality-html5.html)
 by [marmelab](https://marmelab.com/) featuring [François Zaninotto](https://twitter.com/francoisz).
-It explain how to code a full application on phone! Step by Steps, with explaination and videos.
+It explain how to code a full application on phone! Step by Steps, with explanation and videos.
 Very great! the perfect step if you want to start writing AR application today.
 
 ## Advanced guides