dillon1000/react

Fiber side-effects

This adds tracking of side-effects that gets scheduled during an
update.

As the tree gets reconciled, the side-effectful fibers are linked
together in an ordered singly linked list. That way we can walk
the linked list to commit only the work that needs to be
synchronous - quickly.

We also store first and last nodes within a fiber. That
way when we reuse an already processed subtree, we can reuse that
subset of the linked list.