Optimistic UI Updates

There are places where we can reasonably predict the server response in our app, like when we are logged in and we star a take or follow/unfollow a user. The client side UI state can be updated before the server responds in these cases, and then reverted in the case of a failure response from the server. This will give our app a much snappier feel at a low cost.

(thanks to https://egghead.io/lessons/react-course-overview-optimistic-ui-updates-in-react)

See ReactionContainer.tsx for these scenarios.