Add a context menu action for instantiating and duplicating main components

At the moment, pressing Ctrl+D on a main component will create an instance if the original component does not have variants. If it has variants, Ctrl+D will instead create a second main component with the same variants (as do Alt+Drag and Copy+Paste). While this reflects the functions that I use most often, I also want to do the other from time to time: duplicating single-variant components or instantiating multi-variant components. All other ways to achieve this currently require lots of clicks and/or typing. It would be really helpful and imo intuitive if both actions were possible via the context menu (right-clicking on the main component).