Add ControlledInput component

Showcases both useState and useEffect very nicely

snippets/useClickInside.md

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+---
+title: useClickInside
+tags: hooks,effect,event,intermediate
+---
+
+A hook that handles the event of clicking inside the wrapped component.
+
+- Create a custom hook that takes a `ref` and a `callback` to handle the `click` event.
+- Use the `React.useEffect()` hook to append and clean up the `click` event.
+- Use the `React.useRef()` hook to create a `ref` for your click component and pass it to the `useClickInside` hook.
+
+```css
+.click-box {
+  border: 2px dashed orangered;
+  height: 200px;
+  width: 400px;
+  display: flex;
+  justify-content: center;
+  align-items: center;
+}
+
+p {
+  border: 2px solid blue;
+  padding: 16px;
+}
+```
+
+```jsx
+const useClickInside = (ref, callback) => {
+  const handleClick = e => {
+    if (ref.current && ref.current.contains(e.target)) {
+      callback();
+    }
+  };
+  useEffect(() => {
+    document.addEventListener('click', handleClick);
+    return () => {
+      document.removeEventListener('click', handleClick);
+    };
+  });
+};
+
+function ClickBox({ onClickInside }) {
+  const clickRef = useRef();
+  useClickInside(clickRef, onClickInside);
+  return (
+    <div className="click-box" ref={clickRef}>
+      <p>Hello Click Me Inside!</p>
+    </div>
+  );
+}
+```
+
+```jsx
+ReactDOM.render(
+  <ClickBox onClickInside={() => alert('click inside')} />,
+  document.getElementById('root')
+);
+```