Cobblemon Raid Den Keys

Adds seven tiered keys to add as costs to raid dens.

Keys increase in cost from TIER_ONE to TIER_SEVEN.

Simple as that, tiny mod, I know.

If you are a mod author and are looking for a datapack for adding the key costs to all existing raids, you can find the latest here: https://discord.com/channels/1355016729679499284/1464825791312302202/1464825791312302202