Implement Initialize method in Editor class and override in derived editors

src/app/editor/graphics/screen_editor.cc

@@ -26,6 +26,8 @@ using core::Renderer;
 
 constexpr uint32_t kRedPen = 0xFF0000FF;
 
+void ScreenEditor::Initialize() {}
+
 absl::Status ScreenEditor::Update() {
   if (ImGui::BeginTabBar("##ScreenEditorTabBar")) {
     if (ImGui::BeginTabItem("Dungeon Maps")) {