Implement basic UI support

[GeoB99]

As of right now the mod lacks any UI/UX for multiplayer interaction. This issue report is created to keep track of TODOs progress of the UI framework of the mod.

TODO

• Implement "Multiplayer" settings under Settings of the game
• Implement a server list UI. This list shows up when one clicks "Multiplayer"
• Implement the "Open to LAN" UI option, which it'll replace the Co-Op button

[necoarcc]

oops, merging my pr closed this. pretty sure this isn't complete