Add dom::blink and component::Input

examples/input/main.cpp

ftxui/CMakeLists.txt

ftxui/include/ftxui/README.md

ftxui/include/ftxui/component/input.hpp

ftxui/include/ftxui/dom/elements.hpp

ftxui/include/ftxui/event.hpp

ftxui/include/ftxui/screen.hpp

ftxui/src/ftxui/component/input.cpp

ftxui/src/ftxui/event.cpp

ftxui/src/ftxui/screen.cpp

ftxui/src/ftxui/screen_interactive.cpp