Slate Discord Bridge

• Voice messages recorded with Slate Chat go to Discord as an audio file under the player's name.
• GIFs from Discord's GIF picker show in Minecraft again (the picker moved from Tenor to KLIPY); for now as a still picture.
• The face a player's messages are posted under follows their current skin at once; it could lag a day behind. Offline-mode players are looked up by name.
• Chat is picked up after other mods had their say on it: a line a mod re-sends as a system message (No Chat Reports does) goes to Discord exactly once, and a muted line does not go.
• New mod icon.

Slate modules need the Slate Core of their own version: update all of them together.