fix: typo (#4)

Author: matiasbaldanza

exercises/README.mdx

@@ -10,7 +10,7 @@ understanding of how they work behind the scenes. We'll be building `useState`
 and `useEffect`.
 
 <callout-warning>
-	This will of course not be as rigerous as the official implementation.
+	This will of course not be as rigorous as the official implementation.
 </callout-warning>
 
 You're gonna rock with this! Let's get going!