testbed: work in progress (if only I had more time these days...)

testbed/system/imgui_system.cpp

@@ -0,0 +1,16 @@
+#include <entt/entity/registry.hpp>
+#include <imgui.h>
+#include <system/imgui_system.h>
+
+namespace testbed {
+
+void imgui_system(entt::registry &registry) {
+    ImGui::Begin("testbed");
+
+    // ...
+    static_cast<void>(registry);
+
+    ImGui::End();
+}
+
+} // namespace testbed