Revert "remove mentionable switch since discord can do that now"

This reverts commit 0f003e262d.

source/modules/dtl.rb

@@ -67,11 +67,13 @@ class Mod_DTL < Vrobot4::Module::Module
       ids  = get_notification_roles m, argv[0]
       if m.user.real.role? ids[:dev]
          notif = m.chan.real.server.role ids[:not]
+         notif.mentionable = true
          if argv[1]
             m.reply "#{notif.mention} - #{argv[1].strip}"
          else
             m.reply notif.mention
          end
+         notif.mentionable = false
       else
          m.reply "You don't have permission for that."
       end