Add support for Harmony (#1656)

Harmony is a relatively new (1,5yo) chat protocol with a small community.
This introduces support for Harmony into Matterbridge, using the functionality
specifically designed for bridge bots. The implementation is a modest 200 lines
of code.

vendor/github.com/harmony-development/shibshib/located.go

@@ -0,0 +1,10 @@
+package shibshib
+
+import chatv1 "github.com/harmony-development/shibshib/gen/chat/v1"
+
+type LocatedMessage struct {
+	chatv1.MessageWithId
+
+	GuildID   uint64
+	ChannelID uint64
+}