message: Update docs/howto.md for internal room id
  Update docs/howto.md to let new users know that they should use the internal
  room id when using ``adminme`` script.
diff: @@ -18,6 +18,9 @@ is formatted as https://discordapp.com/channels/``guildid``/``channelid``
  * ``npm run adminme -- -r '!AbcdefghijklmnopqR:example.com' -u '@Alice:example.com' -p '100'``
  * Run ``npm run adminme -- -h`` for usage.
  +Please note that ``'!AbcdefghijklmnopqR:example.com'`` is the internal room id and will always begin with ``!``.
  +You can find this internal id in the room settings in Riot.
  +
  ### Migrate to postgres from sqlite
  * Stop the bridge.
  * Create a new database on postgres and create a user for it with a password.
  