BREAKING CHANGE:
The icon gdoc_telescope was removed. If you are using this icon you have to replace it.
Build-in icons are prefixed with gdoc_ now. If you use built-in icons in e.g. menus you have to rename these references!
* feat: add optional extra menu to site navigations
* add extra menu documentation
* rename menu to menu-extra
* feat: add optional extra menu to site navigations
* add extra menu documentation
* rename menu to menu-extra
* fix spellcheck