Investigate unmounting effects not running

[jchavarri]

Thanks to @benschinn we have support for useEffect and useLayoutEffect 🎉

One thing that remains to investigate are the unmount effects, which don't see to be running at the moment.

This can be seen in this line

https://github.com/jchavarri/rroo/blob/cfd84885338f055c6e1285f586de2f51043bb8b8/bin/UseEffect.re#L20-L22

that does not appear in the console.

In order to "bridge" the returned value with the effect we would have to, from React.js file:

• read the returned value from the callback
• check if it's None (0) or Some (array)
• if it's Some, take the callback "from inside", convert to jsoo and return it as part as the React.useEffect function.