Revert examples change + add doc.

examples/component/renderer.cpp

@@ -3,18 +3,12 @@
 // the LICENSE file.
 #include <memory>  // for shared_ptr, allocator, __shared_ptr_access
 
-#ifndef FTXUI_BUILD_MODULES
 #include "ftxui/component/captured_mouse.hpp"  // for ftxui
 #include "ftxui/component/component.hpp"       // for Renderer, Button, Vertical
 #include "ftxui/component/component_base.hpp"  // for ComponentBase
 #include "ftxui/component/screen_interactive.hpp"  // for ScreenInteractive
 #include "ftxui/dom/elements.hpp"  // for operator|, Element, text, bold, border, center, color
 #include "ftxui/screen/color.hpp"  // for Color, Color::Red
-#else
-import ftxui.component;
-import ftxui.dom;
-import ftxui.screen;
-#endif
 
 int main() {
   using namespace ftxui;