Add support for nxxm.

[nxxm](https://nxxm.github.io)

include/ftxui/component/container.hpp

@@ -0,0 +1,45 @@
+#ifndef FTXUI_COMPONENT_CONTAINER_HPP
+#define FTXUI_COMPONENT_CONTAINER_HPP
+
+#include "ftxui/component/component.hpp"
+
+namespace ftxui {
+
+// A component where focus and events are automatically handled for you.
+// List of container:
+//
+// Please use HorizontalContainer or VerticalContainer.
+class Container : public Component {
+ public:
+  static Container Vertical();
+  static Container Horizontal();
+  static Container Tab(int* selector);
+
+  ~Container() override = default;
+
+  // Component override.
+  bool OnEvent(Event event) override;
+  Element Render() override;
+  Component* ActiveChild() override;
+
+ protected:
+  // Handlers
+  using EventHandler = bool (Container::*)(Event);
+  bool VerticalEvent(Event event);
+  bool HorizontalEvent(Event event);
+  bool TabEvent(Event event) { return false; }
+  EventHandler event_handler_;
+
+  using RenderHandler = Element (Container::*)();
+  Element VerticalRender();
+  Element HorizontalRender();
+  Element TabRender();
+  RenderHandler render_handler_;
+
+  int selected_ = 0;
+  int* selector_ = &selected_;
+};
+
+}  // namespace ftxui
+
+#endif /* end of include guard: FTXUI_COMPONENT_CONTAINER_HPP */