forgot first virtual bool Load() in Application.hpp (#118)

I noticed the example had another inconsistency using
std::string_view vs std::string library

Author: blandrice

docs/1-introduction/1-1-getting-started/1-1-1-hello-window.md

@@ -226,6 +226,7 @@ public:
 protected:
     virtual void Cleanup();
     virtual bool Initialize();
+    virtual bool Load() = 0;
     virtual void Render() = 0;
     virtual void Update() = 0;