Support scheduled maintanence window/scilent hours

[codenio]

Is your feature request related to a problem? Please describe. In case of having a scheduled maintaince window or scilent hours, botkube can be muted from pushing alerts to channels.

Describe the solution you'd like Cron based maintance window support configurable thorugh config, botkube command

Additional context Major time based control and automation can be added subsiquently