Modal dialogs without React (or JavaScript)

We had an accessibility review last winter where we were getting complaints that our React-based modals were not completely hiding content from accessibility checkers and screen readers. <dialog> turned out to be a great solution when we rebuilt our <Modal>(s) around them. There is a little mismatch between the edge-triggered events of the <dialog> and the way React wants to be level-triggered but it was not hard to reconcile.