Improve cmake and GUI (#13)

+ Packaging and CI for Windows, Mac, Linux
+ Debian package, NSIS Windows installer, OSX appbundle
+ Example application using libqtk
+ Component installation for `qtk`, `libqtk`, or `collection` with cmake

src/app/treeview.h

@@ -0,0 +1,73 @@
+/*##############################################################################
+## Author: Shaun Reed                                                         ##
+## Legal: All Content (c) 2023 Shaun Reed, all rights reserved                ##
+## About: TreeView plugin for scene hierarchy                                 ##
+##                                                                            ##
+## Contact: shaunrd0@gmail.com  | URL: www.shaunreed.com | GitHub: shaunrd0   ##
+################################################################################
+*/
+
+#ifndef TREEVIEW_H
+#define TREEVIEW_H
+
+#include <QDesignerCustomWidgetInterface>
+#include <QDesignerExportWidget>
+#include <QDockWidget>
+
+#include <qtk/scene.h>
+#include <QTreeWidgetItem>
+
+namespace Ui {
+  class TreeView;
+}
+
+namespace Qtk {
+  class TreeView : public QDockWidget {
+      Q_OBJECT
+
+    public:
+      /*************************************************************************
+       * Constructors / Destructors
+       ************************************************************************/
+
+      explicit TreeView(QWidget * parent = nullptr);
+
+      ~TreeView();
+
+      /*************************************************************************
+       * Public Methods
+       ************************************************************************/
+
+      /**
+       * Updates the QTreeWidget with all objects within the scene.
+       * @param scene The scene to load objects from.
+       */
+      void updateView(const Scene * scene);
+
+    public slots:
+      /**
+       * Focus the camera on an item when it is double clicked.
+       * Triggered by QTreeWidget::itemDoubleClicked signal.
+       *
+       * @param item The item that was double clicked
+       * @param column The column of the item that was double clicked.
+       *    This param is currently not used but required for this signal.
+       */
+      void itemFocus(QTreeWidgetItem * item, int column);
+
+    private:
+      /*************************************************************************
+       * Private Members
+       ************************************************************************/
+
+      Ui::TreeView * ui;
+
+      /**
+       * The name of the scene last loaded by this TreeWidget.
+       * Used to load object data from a target scene.
+       */
+      QString mSceneName;
+  };
+}  // namespace Qtk
+
+#endif  // TREEVIEW_H