New authentication method for apps: GetAuthTicketForWebApi

[therepower]

hello, Some newer games use GetAuthTicketForWebApi instead of GetAuthTicket to authenticate via steam, which was implemented to SteamWorks in 2023.

The functions in appauth.js doesn't support this yet.

Could you implement it if possible?

https://partner.steamgames.com/doc/api/ISteamUser#GetAuthTicketForWebApi