Add a caches object to component options

[rglover]

Building an SPA and I'm trying to depend on a cache.get() call in my render. Technically this works, but it doesn't trigger a re-render. Components should have an optional caches property that can be set like this...

const App = ui.component({
  caches: {
    app: cache('app'),
  },
  ...
});

The idea being that internally, Joystick can listen to the on('change') handle and trigger a re-render of the component whenever this updates. Might be a little messy so may want some way to configure it, but would come in handy as the only alternative at the moment is copying global state over to local state 😢.