Change debug dump file extension to .json

src/debugging/debugJS.js

@@ -104,7 +104,7 @@ App.Debug.dumpGameState = function () {
 			if (oldHandler) {
 				oldHandler(save);
 			}
-			downloadToFile(JSON.stringify(save, null, 2), save.id + ".js", "text/plain");
+			downloadToFile(JSON.stringify(save, null, 2), save.id + ".json", "text/plain");
 		}
 		SugarCube.Save.serialize();
 	} finally {