I want to know how I can create a completely custom texture atlas and how do I initialize it? As I understand in version 1.21 the atlas system is now fully described in json/mcmeta files and during client initialization an atlas is created from the listed texture files.

I’m begun in fabric modding and i want for my mod to load a resource pack when the mod is loaded.
Then, i found in the fabric api a code, i took for my mod here.

i cant register a new item with Registry.ITEM