dillon1000/react

pure (#13748)

* pure

A higher-order component version of the `React.PureComponent` class.
During an update, the previous props are compared to the new props. If
they are the same, React will skip rendering the component and
its children.

Unlike userspace implementations, `pure` will not add an additional
fiber to the tree.

The first argument must be a functional component; it does not work
with classes.

`pure` uses shallow comparison by default, like `React.PureComponent`.
A custom comparison can be passed as the second argument.

Co-authored-by: Andrew Clark <[email protected]>
Co-authored-by: Sophie Alpert <[email protected]>

* Warn if first argument is not a functional component