Add UI after quitting

[dfabulich]

When you quit a game, the UI just locks up; it's not obvious to users what to do at that point.

Lectrote handles this by popping up a banner, "The game session has ended." Spatterlight pops up a "Game over" message that fades away.

I don't think either of these options are awesome. I think it should pop up a dialog offering to let you restart, and maybe toss in a link to IFDB for good measure…?

[dfabulich]

Apparently this varies by interpreter! Parchment does show a "The game session has ended" banner in Glulx games, from Quixe. https://github.com/erkyrath/quixe/blob/master/src/quixe/gi_load.js#L120

But Z-machine games, TADS games, and Hugo games just lock up, as I said.