remove potential race condition updating the ref

[timmy-wright]

Turns out you can assign to react refs during a render cycle, so this PR does that instead of using a layout effect to update the ref. This removes the chance that something happens between the useEvent hook being called and the useLayoutEffect occurring.

[vain0x]

// not sure this I like assigning to a ref during the method call, but React recommends it for certain circumstances:
...
ref.current = fn;

According to Caveats of useRef:

• Do not write or read ref.current during rendering, except for initialization. This makes your component’s behavior unpredictable.

doing ref.current = fn during rendering doesn't seem to be allowed. See also a comment.