Add command /lock and /unlock to lock and unlock a channel from user messages and reactions.

[vxern]

The /unlock command does not take any parameters.
The /lock command would take the following parameters:

• duration (Options + Autocomplete, Optional) - Specify the duration of time that the channel would remain locked for.
  • TODO: What default options should the command support?

Notes:

• The /lock command when run on a locked channel and without the duration parameter would function identically to /unlock.
• The /lock command when run on a locked channel and with the duration parameter would upgrade/downgrade the duration of time that the channel is locked for.
• The /unlock command would display a confirmation prompt asking the user to confirm that they want to unlock the channel. This is to prevent a possible conflict occurring when two guides try to lock a channel one after the other, essentially undoing the effect.