Adds two blind box items:
- Blind Box: right click to draw one random registered item or block item.
- Custom Blind Box: right click to draw a weighted reward from
config/BlindBox.cfg.
The config supports namespace keys such as minecraft:item.diamond=1;weight=3.
It also generates config/BlindBox.reference.cfg as one enum-style lookup table for currently registered item, block, and enchantment keys.