List the missing channel modes in the 004 reply (closes #238)

The channel-modes parameter of RPL_MYINFO left out modes that each
transport's MODE accepts. The IRC listener now sends Himnostv, adding
H, i, o and v. The HTTP API now sends Hbiklmnostv, adding H, b and v.
Each transport keeps its own list, because they accept different
modes. The tests compare the whole parameter, so a missing or extra
mode fails them. The README and the schema notes show the new HTTP API
list.

Model: opus-5-5

internal/ircserver/conn.go

@@ -605,7 +605,7 @@ func (c *Conn) deliverWelcome() {
 	)
 	c.sendNumeric(
 		irc.RplMyInfo,
-		c.serverSfx, "neoirc", service.UserModes, "mnst",
+		c.serverSfx, "neoirc", service.UserModes, "Himnostv",
 	)
 	c.sendNumeric(
 		irc.RplIsupport,