Direct messages a user.
There are three possible usages of the
This will send the message to the user that runs the command.
This will send the message to the first mentioned user.
This will send the message to every user with given User ID.
(Type: Snowflake || Flag: Emptiable): The user to whom to send the direct message.
If the command fails to send the message, make sure the user allows dm messages from everyone.