Adding useEffect hook

[zbzalex]

1. add global variable

   let pendingEffects = []

2. cerate a hook and add effects tag

   function useEffect(fn, deps) {
           const hook = {
               tag: "EFFECT",
               fn,
               deps,
           }
   
           wipFiber._hooks.push(hook)
           hookIndex++
   }

3. modify performUnitOfWork function

   if (isFunctionComponent) {
   ...
   Object .keys(wipFiber._hooks)
                   .filter(hookIndex => wipFiber._hooks[hookIndex].tag === "EFFECT")
                   .forEach(hookIndex => {
                       const oldHook =
                           wipFiber.alternate &&
                           wipFiber.alternate._hooks &&
                           wipFiber.alternate._hooks[hookIndex]
   
                       const hook = wipFiber._hooks[hookIndex]
                       const depsChanged = (prev, next) => (_, index) => prev[index] !== next[index];
                       if (hook.deps.length === 0 && !oldHook
                           || oldHook && (oldHook.deps.length !== hook.deps.length
                               || oldHook && hook.deps.filter(depsChanged(oldHook.deps, hook.deps)).length !== 0)) {
                           pendingEffects.push(hook.fn)
                       }
                   })
   ...

4. go to commitRoot function

...
pendingEffects.forEach(it => it()) // call pending effects after render

[zbzalex]

Modification project https://github.com/zbzalex/react-lite