Added Steam Multiplayer (with a few tweaks and fixes)

Writing this post myself this time, I added a way to use Steam's P2P Multiplayer in the lobby configuration in case the default setting doesn't work.

Also some tweaks:

• fixed an infinite Bastolic set interaction
• fixed pvp
• added visual popup for +1 diamonds when merging divines

The new system may cause some issues with the coop, so feel free to report any issues here in discord or add me on steam.