New skyboxrenderer + moved meshrenderer inside engine and out from main to clean that up

JulietApp/main.h

@@ -43,6 +43,7 @@ class JulietApplication : public Juliet::IApplication
     Juliet::HotReloadCode     GameCode         = {};
     Juliet::GraphicsPipeline* GraphicsPipeline = {};
     Juliet::Texture*          DepthBuffer      = {};
+    Juliet::GraphicsPipeline* SkyboxPipeline   = {};
     Juliet::Arena*            GameArena        = nullptr;
     Juliet::Arena*            GameScratchArena = nullptr;