feat: add play / editor mode

lightkeeper/include/Lightkeeper.h

@@ -1,6 +1,7 @@
 #ifndef LIGHTKEEPER_H
 #define LIGHTKEEPER_H
 
+#include <optional>
 #include <string>
 
 #include <destrum/App.h>
@@ -28,6 +29,7 @@ public:
 
     void onWindowResize(int newWidth, int newHeight) override;
     void customWindowsMenu() override;
+    void onPlayModeChanged(bool nowPlaying) override;
 
 private:
     void setupSkybox();
@@ -53,6 +55,7 @@ private:
     void submitColliderDebugLines();
 
     Camera camera{glm::vec3(0.f, 0.f, -5.f), glm::vec3(0, 1, 0)};
+    std::optional<Camera> editorCamera;
 
     std::unique_ptr<CubeMap> skyboxCubemap;
     MainSceneObjects mainScene{};