feat: Multiple border style. (#202)

examples/dom/separator_style.cpp

@@ -0,0 +1,41 @@
+#include <ftxui/dom/elements.hpp>  // for text, operator|, vbox, border, Element, Fit, hbox
+#include <ftxui/screen/screen.hpp>  // for Full, Screen
+#include <iostream>
+#include <memory>  // for allocator
+
+#include "ftxui/dom/node.hpp"    // for Render
+#include "ftxui/screen/box.hpp"  // for ftxui
+
+int main(int argc, const char* argv[]) {
+  using namespace ftxui;
+
+  auto document = vbox({
+      vbox({
+          text("separatorLight"),
+          separatorLight(),
+          hbox(text("left"), separatorLight(), text("right")),
+      }) | borderLight,
+
+      vbox({
+          text("separatorHeavy"),
+          separatorHeavy(),
+          hbox(text("left"), separatorHeavy(), text("right")),
+      }) | borderHeavy,
+
+      vbox({
+          text("separatorDouble"),
+          separatorDouble(),
+          hbox(text("left"), separatorDouble(), text("right")),
+      }) | borderDouble,
+  });
+
+  auto screen =
+      Screen::Create(Dimension::Fit(document), Dimension::Fit(document));
+  Render(screen, document);
+  screen.Print();
+  std::cout << std::endl;
+}
+
+// Copyright 2020 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.