This change adds a new dialog component to Ink. It uses the new(ish)

<dialog> element, which comes with a bunch of advantages. It can be

shown as either a modal or non-modal.
The dialog has three areas that can be customized: the title, the body,

and actions. Actions can be separated into primary (right-aligned) and

secondary (left-aligned).
Actions can be specified either as regular buttons (or other elements),

or as a special DialogAction. The DialogAction exists to prevent

boilerplate for common cases, and has two modes: close or callback. If

an action uses a callback and said callback returns a promise, all of

the dialog's actions will be disabled while that promise runs, and the

action that triggered it will be shown as busy.

Used dialog in storybook.
Used this from some code in Review Board.