Dialog element

Method of easily creating custom dialog boxes to display to the user with modal or non-modal options. Also includes a `::backdrop` pseudo-element for behind the element.

elementinternals api: ariamodal

element api: ariamodal

htmldialogelement api: showmodal

window api: showmodaldialog

css selector: `:modal`

html element: iframe: sandbox: `sandbox="allow-modals"`