Added Steam Multiplayer (with a few tweaks and fixes)

[p]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.

[/p]