Add support for nxxm.

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

include/ftxui/component/toggle.hpp

@@ -0,0 +1,33 @@
+#ifndef FTXUI_COMPONENT_TOGGLE_H_
+#define FTXUI_COMPONENT_TOGGLE_H_
+
+#include "ftxui/component/component.hpp"
+#include <functional>
+#include <string>
+
+namespace ftxui {
+
+class Toggle : public Component {
+ public:
+  // Constructor.
+  ~Toggle() override = default;
+
+  // State.
+  int selected = 0;
+  std::vector<std::wstring> entries = {L"On", L"Off"};
+
+  Decorator focused_style = inverted;
+  Decorator selected_style = bold;
+  Decorator normal_style = dim;
+
+  // Callback.
+  std::function<void()> on_change = [](){};
+
+  // Component implementation.
+  Element Render() override;
+  bool OnEvent(Event) override;
+};
+
+}  // namespace ftxui::Component
+
+#endif /* end of include guard: FTXUI_COMPONENT_TOGGLE_H_ */