fixed minor typo (#236)

Author: bensonzachariah

exercises/README.mdx

@@ -6,7 +6,7 @@
 this workshop. I'll be there to tell you what our users want and to help you
 understand the requirements of the tasks you'll be working on.
 
-React hooks are an critical part of React development. You can think of them as
+React hooks are a critical part of React development. You can think of them as
 atoms to the React component molecule. Everything outside of basic rendering
 can be done with hooks.