Help update @reach/dialog to be compatible with React 18, or migrate to another compatible backing component

[frankieyan]

We rely on Reach-UI's Dialog component to power our Modal.

In Todoist, there are 11 modals built using the Reactist Modal, and 27 in Twist. Todoist also pulls in @reach/dialog directly and uses it to implement another 27 modals, bringing the total to 38.

There is an opportunity to contribute back to Reach-UI - its author is looking for help in making the component suite React 18 compatible (ref).

An alternative we can consider is to use Ariakit's Dialog. It works with React 18 and we already have it as a dependency after migrating other Reakit-backed components over. Ideally, we pick one backing library to power Reactist as there are shared dependencies and lower-level components each of these components use.

Twist discussion: https://twist.com/a/1585/ch/190200/t/3686215/