Biomes O' Plenty Nether BGM

Metadata:

• Added artist info for the music toasts so they now read as "LudoCrypt - " instead of "Biomes O' Plenty - "

• Made the flavor text for the supported version range more distinct

• The pack.mcmeta is up to date with the new format changes (pack_format is now 64 aka 1.21.8 and supported_formats minimum is now 15 aka 1.20, but it still retains all backwards-compatibility)