This patch provides the basic components needed for developers to create
consistent wizard interface experiences in their applications.
`WizardDialog` provides the dialog frame for the wizard, handling navigation
and presentation.
`AbstractWizardPage`s form the base class of Wizard pages, which are
pushed onto the `WizardDialog` page stack via `WizardDialog::push_page`.
`CoverWizardPage` and `WizardPage` are provided to ease the creation of
Wizard interfaces consistent with the Serenity visual language.
