Add a command that Broadcasts strike times (and update them)

[jopika]

Add a command that allows admins to schedule strike time announcements to let the bot mention them automatically when the time is.

NOTE: All times and Dates should be in JST

!AddStrikeTime [date] [time] [name=""] - Adds strike time announcement on [date] at [time] with an optional name for the strike time
!AddRepeatingStrikeTime [time] [name=""] - Adds strike time announcement that repeats at [time] every day with an optional name for the strike time
!ListStrikeTime - Lists the strike times (/dates) and if they are repeating or not
!NextStrikeTime - Prints the next strike time, and how long it is until
!RemoveStrikeTime [name] - Removes the strike time from the announcement queue