feat(viewport): add camera class

src/gui/viewport/ViewportGLWidget.h

@@ -3,6 +3,7 @@
 #include <QOpenGLWidget>
 #include <iostream>
 #include <QOpenGLFunctions_3_2_Core>
+#include "gui/viewport/GLCamera.h"
 
 class ViewportGLWidget : public QOpenGLWidget, protected QOpenGLFunctions_3_2_Core
 {
@@ -11,7 +12,7 @@ public:
     QSize sizeHint() const override { return QSize(-1, -1); }
     GLuint vao;
     GLuint shaderProgram;
-    float angle_ = 0.0f;
+    GLCamera camera_;
 
 protected:
     void initializeGL() override;