"Custom Data Components": `appendTooltip` is deprecated

[electricsteve]

In this section it mentions you need to implement appendTooltip, but since 1.21.5 that's deprecated and even on the old wiki it says you need to use Fabric Api. Consider changing this section.

[electricsteve]

Also since 1.21.2 you now need to set the item registry key so the code won't work.

[electricsteve]

Another thing is the protected initialize method wouldn't actually be accessible by the mod initializer if it's a package higher, unless I'm missing something.