refactor: state into namespace

src/engine.cpp

@@ -75,11 +75,11 @@ void Engine::initialize()
 	}
 
 	// Initialize default shader
-	State::default_shader_ =
+	state::default_shader =
 	    std::make_shared<Shader>("data/vertex.glsl", "data/fragment.glsl");
-	if (std::strlen(State::default_shader_->error()) > 0) {
+	if (std::strlen(state::default_shader->error()) > 0) {
 		std::cerr << "Failed to initialize shaders: "
-			  << State::default_shader_->error() << "\n";
+			  << state::default_shader->error() << "\n";
 	}
 }