v2.3.0-beta.1

• Re-added RPC handler listeners.
• Added support for Ask to Join, with a config option to disable it.
• Added DiscordRP_TestJoin console command to join a game via invite code (for testing).
• Changed to new Discord Game SDK.
• API's FormatText function now returns "" instead of null if given an empty string.
• Removed automatic Mac and Linux setup because it's no longer needed.
• ACTUALLY fixed potential error when generating presence in co-op.