server: Implement TAGMSG draft command

irc/help.go

@@ -300,6 +300,12 @@ Gives the given user a new nickname.`,
 		text: `SCENE <target> <text to be sent>
 
 The SCENE command is used to send a scene notification to the given target.`,
+	},
+	"tagmsg": {
+		text: `@+client-only-tags TAGMSG <target>{,<target>}
+
+Sends the given client-only tags to the given targets as a TAGMSG. See the IRCv3
+specs for more info: http://ircv3.net/specs/core/message-tags-3.3.html`,
 	},
 	"quit": {
 		text: `QUIT [reason]