== Issue
When the dialog is first opened, the focus is not set in a place that makes it easy to access the content in the rest of the dialog, and it's possible to navigate components hidden behind the dialog.
=== Resources
https://www.w3.org/WAI/ARIA/apg/patterns/dialog-modal/
=== Developer notes
While `aria-modal="true"` removes requirement of putting `aria-hidden` on background content, as the `aria-modal` informs assistive technologies that content outside a dialog is `inert`, it's the safe way to have both attributes in use on the dialog and the background content elements.
The escaping of dialogs by pressing <ESC> has already been part since the original Dialog implementation.
== Acceptance Criteria
[ ] Add `aria-modal="true"` to the `role="dialog"` element.
[ ] Focus on initial dialog open should work in a predictable way.
[ ] Users should not be able to interact with content behind the dialog when open.
[x] ~~The user should always have a way to exit the dialog using keyboard navigation.~~ In initial implementation