Update README.md

Author: jstarry

examples/todomvc/README.md

@@ -1,6 +1,6 @@
 ## Yew TodoMVC Demo
 
-This it an implementationt of [TodoMVC](http://todomvc.com/) app.
+This is an implementation of [TodoMVC](http://todomvc.com/) app.
 
 Unlike other implementations, this stores the full state of the model,
 including: all entries, entered text and chosen filter.