Remove NXXM. Execute IWYU. (#397)

.nxxm/deps

README.md

examples/component/button_style.cpp

examples/component/maybe.cpp

examples/dom/hflow.cpp

examples/dom/html_like.cpp

examples/dom/vflow.cpp

include/ftxui/component/component_options.hpp

include/ftxui/component/screen_interactive.hpp

include/ftxui/screen/screen.hpp

src/ftxui/component/button_test.cpp

src/ftxui/component/menu.cpp

src/ftxui/component/radiobox.cpp

src/ftxui/component/terminal_input_parser.hpp

src/ftxui/dom/blink_test.cpp

src/ftxui/dom/bold_test.cpp

src/ftxui/dom/dbox.cpp

src/ftxui/dom/dim_test.cpp

src/ftxui/dom/underlined_test.cpp

src/ftxui/dom/util.cpp