[GUI] Add ability to select a recently-loaded file to the welcome screen

[tturocy]

This feature request is for...

Gambit GUI

Requested enahancement or feature

A useful convenience would be to have access to the MRU file list in the opening Welcome screen, alongside being able to load a file (which just drops you into the file picker in the most recently used directory).

[d-kad]

@rahulsavani -- please let me know if you are already working on this, if not, I can start it now

[rahulsavani]

@d-kad

I have not started on this, so please go ahead.