Run IWYU (#450)

examples/component/modal_dialog.cpp

iwyu.imp

src/ftxui/component/animation_test.cpp

src/ftxui/component/button_test.cpp

src/ftxui/component/collapsible_test.cpp

src/ftxui/component/component_test.cpp

src/ftxui/component/container_test.cpp

src/ftxui/component/input_test.cpp

src/ftxui/component/menu_test.cpp

src/ftxui/component/modal_test.cpp

src/ftxui/component/radiobox_test.cpp

src/ftxui/component/receiver_test.cpp

src/ftxui/component/resizable_split_test.cpp

src/ftxui/component/screen_interactive_test.cpp

src/ftxui/component/terminal_input_parser_test.cpp

src/ftxui/component/terminal_input_parser_test_fuzzer.cpp

src/ftxui/component/toggle_test.cpp

src/ftxui/dom/blink_test.cpp

src/ftxui/dom/bold_test.cpp

src/ftxui/dom/border_test.cpp