* chore(docs): migrate & document all Page events
Rather than a generic `Events.ts` file we can instead document events as
an enum within each individual class. It's easier to document and work
with, and it's clearer where events originate from.
This PR starts exploring the Page class and how to best document it. It explores how best to document events in the system, and I think pulling them out into an `enum` is the best solution here. It lets us end up with a page of docs that explicitly lists all the events the page class can ever emit.