Add support for nxxm.

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

src/ftxui/component/component.cpp

@@ -0,0 +1,56 @@
+#include "ftxui/component/component.hpp"
+#include <assert.h>
+
+namespace ftxui {
+void Component::Detach() { if (!parent_) return; auto it = std::find(std::begin(parent_->children_),
+                      std::end(parent_->children_), this);
+  parent_->children_.erase(it);
+
+}
+
+void Component::Attach(Component* parent) {
+  Detach();
+  parent_ = parent;
+  parent_->children_.push_back(this);
+}
+
+void Component::Add(Component* child) {
+  child->Attach(this);
+}
+
+Component::~Component() {
+  Detach();
+}
+
+bool Component::OnEvent(Event event) {
+  for(Component* child : children_) {
+    if (child->OnEvent(event))
+      return true;
+  }
+  return false;
+}
+
+Component* Component::ActiveChild() {
+  return children_.empty() ? nullptr : children_.front();
+}
+
+Element Component::Render() {
+  if (children_.size() == 1)
+    return children_.front()->Render();
+
+  return text(L"Not implemented component");
+}
+
+bool Component::Focused() {
+  Component* current = this;
+  for(;;) {
+    Component* parent = current->parent_;
+    if (!parent)
+      return true;
+    if (parent->ActiveChild() != current)
+      return false;
+    current = parent;
+  }
+}
+
+}  // namespace ftxui