Add documentation for options.

examples/component/menu_style.cpp

include/ftxui/component/component_options.hpp

include/ftxui/util/ref.hpp

src/ftxui/component/checkbox.cpp

src/ftxui/component/menu.cpp

src/ftxui/component/radiobox.cpp

src/ftxui/component/toggle.cpp

src/ftxui/dom/util.cpp