Add support for cookie-js on the client and offer an easy-to-use API

[rglover]

We already have cookie access on the server via req.cookies, but it'd be nice if we could set/read cookies on the client, too. cookie-js is a solid solution for this, but it'd be nice if you could have that as a dependency (or write your own) and just do import { cookies } from '@joystick.js/ui and then call something like cookies.get() or cookies.set().