mention target

[KT-71]

command ".recheck" mention target more then 20 will throw TalkException from idk where

fix: command.js>Command>mention(listMember)

        return {
            names: mentionStrings.slice(1),
            cmddata: { MENTION: `{"MENTIONEES":[${mentionMember.slice(0, 20)}]}` }
        }