auto generated items.yml for 1.21.R3 and 1.21.4

updated items_1.21.3.yml and items_1.21.R2.yml (auto-generated).

This automatically generated list of tabs and items maintains the order of appearance.

includes items .yml file for 1.21.1 (for both Spigot and paper).

including the auto-generated items.yml file for 1.20.R3.

includes auto-generated items.yml files from 1.20.4

The auto-generation code has been fixed and all tab name entries have been converted to lowercase.

for instance: "Building Blocks:" -> "building_blocks:"