Pause Day Cycle

This is a very small update that doesn't bring any new features, but does address two minor (theoretical) bugs that never (to the best of my knowledge) caused a problem.

• #is_paused is now set to 0 when the pack is first installed, before the time gets paused for the first time. This means that you can now 100% rely on #is_paused (scoreboard pause_day_cycle.dummy) to always have a value of 0 or 1.
• The pack now doesn't rely on its own function tags to implement its functionality. This prevents a subtle bug where a datapack that uses the pause/resume function tags could be placed before Pause Day Cycle in the load order, so when its functions would be called the gamerules wouldn't have been set yet.

It also adds support for the supported_formats mcmeta property, so now it's marked as supporting game versions back to 1.13. I haven't tested on 1.13, but this only uses simple commands, so I'm pretty sure it works. Let me know if it doesn't!

(and it also adds a pack.png, whoops!)