Add note about IP visibility to IRC.html

[LukeMoll]

Libera.chat, like many IRC networks, by default reveals the IP address of the user to anyone sharing a channel with them. This can be avoided by the use of cloaks (on request from Libera staff), a VPN, or an IRC bouncer (like the one offered by HackSoc).

Occasionally new IRC users will get caught out by this, so it would be good to add this information (and links on how to get a cloak or bouncer account) to the page where the IRC channel is advertised.

Clear language is important as this is necessarily for the benefit of users with little or no previous IRC familiarity.

[sersorrel]

(some of) the caveats of cloaks on https://libera.chat/guides/cloaks are probably worth including