Add support for specifying resource pack load order.

[TankObliterator]

I would appreciate it a great deal if pickpack supported changing the resource pack load order.

[TankObliterator]

Closing as this feature is technically implemented now, just as a separate extension.
https://github.com/onebeastchris/PrioPacks/

[onebeastchris]

Reopening, as I'd like to implement that here for users to be able to pick as well