/MSG L WELCOME #channel message
Sets or views the message shown to every user joining the channel. If no message is defined, then the
current channel welcome message is showed. You need to have either +m or +n access for the channel you
intend to change the welcome on. Maximum welcome message lenght is 250 characters.
You can remove the welcome message by using 'remove' as the new welcome message.
Example: /msg l welcome #mychannel Hello and welcome to my channel!
         /msg l welcome #mychannel remove
