Add a search facility to File Explorer and/or expand Search to include non-MindManager file

While I am relieved that the File Explorer feature on the Ribbon still works (the Map Parts option doesn't in MM 22), it would be greatly enhanced if a search facility could be added.

The current search facility could also be extended to add the ability to search all files, and not just MindManager ones.

At the moment, the only option to search from within MindManager is to use the Search facility within Windows File Explorer. There is a slightly circuitous workaround to do this which I describe here, but a "proper" built in search function would be a lot better: https://sociamind.com/2020/05/25/search-all-files-in-mindmanager-with-a-little-help-from-windows/