Rewrite mod details under new UI system.

src/ui/elements/ui_container.cpp

@@ -0,0 +1,14 @@
+#include "ui_container.h"
+
+#include <cassert>
+
+namespace recompui {
+
+    Container::Container(FlexDirection direction, JustifyContent justify_content, Element *parent) : Element(parent) {
+        set_display(Display::Flex);
+        set_flex(1.0f, 1.0f);
+        set_flex_direction(direction);
+        set_justify_content(justify_content);
+    }
+
+};