[cpp] Add Qt Desginer widget plugin examples

cpp/qt/README.md

@@ -0,0 +1,32 @@
+# Cpp
+
+```bash
+shaunrd0/klips/cpp/qt/
+├── designer                    # Using Qt Designer to create application GUI
+├── designer-plugin             # Adding custom widgets as Qt Designer plugins
+├── designer-plugin-collection  # Adding a collection of widget plugins to Qt Designer
+└── README.md
+```
+
+This directory contains a `CMakeLists.txt`, which can be selected to open as a 
+project within your preferred IDE. From there, all nested examples can be built,
+debugged, and ran.
+
+The plugin examples will need to be installed for Qt Designer integration to work.
+On Linux, Qt Designer looks under `/some/path/to/Qt/Tools/QtCreator/lib/Qt/plugins/designer/`.
+On windows or Mac, this path may differ. Unfortunately I don't have these machines to test for myself.
+
+```bash
+cd klips/cpp/qt/designer-plugin-collection
+mkdir build && cd build
+cmake .. && cmake --build . --target install
+```
+
+After installing the plugin collection example above, we can open Qt Creator and navigate to the Designer.
+We should see the custom collection is available within the Designer, and the contents of the widgets render correctly in the application view.
+
+
+![side-panel-view.png](side-panel-view.png)
+
+
+![plugin-render-view.png](plugin-render-view.png)