Update useCounter example to use updater function, As per #47

Author: mpeyper

Diff for: docs/usage/advanced-hooks.md

@@ -15,7 +15,7 @@ import { useState, useCallback } from 'react'
 
 export default function useCounter(initialValue = 0) {
   const [count, setCount] = useState(initialValue)
-  const increment = useCallback(() => setCount(count + 1), [count])
+  const increment = useCallback(() => setCount((x) => x + 1), [])
   return { count, increment }
 }
 ```
@@ -46,7 +46,7 @@ import { useState, useCallback } from 'react'
 
 export default function useCounter(initialValue = 0) {
   const [count, setCount] = useState(initialValue)
-  const increment = useCallback(() => setCount(count + 1), [count])
+  const increment = useCallback(() => setCount((x) => x + 1), [])
   const reset = useCallback(() => setCount(initialValue), [initialValue])
   return { count, increment, reset }
 }

Diff for: docs/usage/basic-hooks.md

@@ -15,7 +15,7 @@ import { useState, useCallback } from 'react'
 
 export default function useCounter() {
   const [count, setCount] = useState(0)
-  const increment = useCallback(() => setCount(count + 1), [count])
+  const increment = useCallback(() => setCount((x) => x + 1), [])
   return { count, increment }
 }
 ```