create entrypoint, add IWYU pragmas

sandbox/src/Application.cpp

@@ -1,5 +1,13 @@
-#include "Test.hpp"
+#include <memory>
+#include <quark.hpp>
 
-int main(int argc, char** argv) {
-	quark::Print();
+class Sandbox :
+	public qk::Application
+{
+public:
+	
+};
+
+std::unique_ptr<qk::Application> qk::CreateApplication() {
+	return std::make_unique<Sandbox>();
 }