BREAKING CHANGES:
- appName → name
- appIcon → icon
- appIconClass → removed (use icon:class)
- homeLink → home
- showDarkToggle → dark
- userName → user
- userAvatar → avatar

New nested attributes:
- icon:class
- dark:class, dark:sun:icon, dark:sun:class, dark:moon:icon, dark:moon:class
- user:class, user:button:class, user:chevron:icon, user:chevron:class, user:menu:class
- avatar:class