Add a demo plugin to xSTUDIO #202
Description
xSTUDIO's C++ API is not fully documented and the intricacies of the CAF message passing system presents a high bar to many developers looking to getting stuck into developing extension plugins.
The exsiting plugin set that are part of the xSTUDIO repo offer plenty of good reference but they don't cover many important implementation examples that developers will typically look for. In particular, developing a performant QML interface that exposes custom data (such as a VFX/Animation prodfuction database front end) and actions such as loading media and creating timelines is not demonstrated in a 'user friendly' way by the existing codebase.
My suggestion (to myself!) is that we add a demo plugin with some mock database data to display in a QML front end, show how to create menu items in xSTUDIO's menu system and also how to interface between C++ and Python plugin components. Other useful features would be template CMake files that show how to setup cmake files to compile and install a plugin with Python, C++ and QML components.