Implementation of /mute command to mute a user for a defined time

[drendog]

To improve channel management and prevent the sending of inappropriate messages, we can implement the /mute command that allows us to mute a user for a specific period of time.

The /mute command should work as follows:

• Only channel administrators should be able to use the /mute command.
• An administrator can mute a specific user using the command /mute @username <time>, where 'time' represents the duration for which the user will be muted (e.g., /mute @misorotterdam 1h mutes user @misorotterdam for 1 hour).
• An administrator can mute a specific user using the command /mute <time> by replying the specific message.