This fixes a bug where creating a page would fail if there were multiple
pages with the same index.
This also changes the store to use a throttled version of
requestAnimationFrame. This should be good for relieving backpressure in
situations where the store is updated many times in quick succession. It
also makes testing a lot easier since it has the mocking logic built in.
### Change Type
- [x] `patch` — Bug Fix
### Release Notes
- Fix a bug where creating a page could throw an error in some
multiplayer contexts.
