promptSteamGuardCode option removed from node-steam-user

[RikkaW]

The promptSteamGuardCode option has been removed from node-steam-user at 1 Dec 2018. https://github.com/DoctorMcKay/node-steam-user/commit/5410debb35a7c1b03322b90941bd5024d8d90843

However package.json always uses the latest node-steam-user. https://github.com/zyfworks/steam-key/blob/v2/package.json#L20

So this part will not work. https://github.com/zyfworks/steam-key/blob/v2/steam.js#L16-L29