Fix some typos for 01.md and 06.md

src/exercise/01.md

@@ -96,7 +96,7 @@ How would you need to change the reducer to make this work?
 
 ### 3. 💯 simulate setState with an object OR function
 
-`this.setState` from class components can also accepts a function. So let's add
+`this.setState` from class components can also accept a function. So let's add
 support for that with our simulated `setState` function. See if you can figure
 out how to make your reducer support both the object as in the last extra credit
 as well as a function callback:

src/exercise/06.md

@@ -3,7 +3,7 @@
 ## Background
 
 [The React DevTools browser extension](https://chrome.google.com/webstore/detail/react-developer-tools/fmkadmapgofadopljbjfkapdkoienihi?hl=en)
-is a must have for any React developer. When you start writing custom hooks, it
+is a must-have for any React developer. When you start writing custom hooks, it
 can be useful to give them a special label. This is especially useful to
 differentiate different usages of the same hook in a given component.
 
@@ -66,7 +66,7 @@ function useCount({initialCount = 0, step = 1} = {}) {
 This is only really useful for situations where computing the debug value is
 computationally expensive (and therefore you only want it calculated when the
 DevTools are open and not when your users are using the app). In our case this
-is not necessary, however go ahead and give it a try anyway.
+is not necessary, however, go ahead and give it a try anyway.
 
 ## 🦉 Elaboration and Feedback