Don't send the welcome message when loading

Don't re-send the welcome message when loading the game if it's already
been sent. This is done by just tracking whether or not we've sent it as
a boolean in the game state, which may be a bit of a hack but should be fine

src/Xanthous/Game/Arbitrary.hs

@@ -28,6 +28,7 @@ instance Arbitrary GameState where
     let _promptState = NoPrompt -- TODO
     _activePanel <- arbitrary
     _debugState <- arbitrary
+    _sentWelcome <- arbitrary
     pure $ GameState {..}