Add emoji endpoint.

endpoints.go

@@ -79,4 +79,6 @@ var (
 	INVITE = func(iID string) string { return API + "invite/" + iID }
 
 	INTEGRATIONS_JOIN = func(iID string) string { return API + "integrations/" + iID + "/join" }
+	
+	EMOJI = func(eID string) string { return API + "emojis/" + eID + ".png" }
 )