Allow clients to open games without joining a world

[haykam821]

This pull request introduces a games screen to clients running Plasmid. From this screen, players can open games provided by mods. When the game closes, the player is returned to the title screen. Like normal worlds, players can open games to LAN.

• [ ] Properly return players to the games screen rather than the multiplayer screen when disconnecting
• [ ] Improve LAN integration
• [ ] Hide the PlasmidGame world from other screens (including the singleplayer and Realms world upload screens)

[Hugman76]

Incredibly handy for minigame development, thank you haykam 👍

[Patbox]

Not sure if full return to title screen is something we would want, through maybe we could provide builtin alternative "lobby mode". Since I imagine it would be useful if it didn't kick everyone out in case of lan games (or games with people playing through E4MC or alike)