Add load state from file

[Former user]

Add a button or key shortcut to load a save state from a file / save state to a file.

[Valtteri Heikkilä]

The site stores the game save states in localStorage. I can add key shortcuts to export/import these to disk. I’ll have to look if it’s possible to export multiple files in same format as FCEUX or if I need to use JSON to save all states in one file.