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.
This is a little bit messy but the basic idea is:
Syntax::Highlighter now has a Syntax::HighlighterClient to talk to the
outside world. It mostly communicates in LibGUI primitives that are
available in headers, so inlineable.
GUI::TextEditor inherits from Syntax::HighlighterClient.
This let us to move GUI::JSSyntaxHighlighter to JS::SyntaxHighlighter
and remove LibGUI's dependency on LibJS.
