dom → screen 关系

文件在 include/ftxui/dom	在 include/ftxui/screen 中引用
canvas.hpp	color.hpp
canvas.hpp	image.hpp
elements.hpp	box.hpp
elements.hpp	color.hpp
elements.hpp	terminal.hpp
linear_gradient.hpp	color.hpp
node.hpp	box.hpp
node.hpp	screen.hpp
requirement.hpp	box.hpp
requirement.hpp	screen.hpp
selection.hpp	box.hpp
selection.hpp	pixel.hpp