Suggestion (Required)

NeoForge changed the package from net.minecraftforge to net.neoforge, so you should do that too.

Published in v9.1.0.

Wouldn`t it be better, instead of adding the net.neoforge package, to release a version for neoforge to provide compatibility through Fabric, Forge, Quilt and NeoForge?
Because of now i would say you only have the compatibility option between Fabric/Quilt and Forge or Fabric/Quilt and NeoForge.

I don't want to support the Forge config classes much longer, will probably drop those from the Api for 1.21.

But allowing NeoForge's config classes to be used on Forge seems like a good idea, it's pretty straight forward to wrap the IConfigSpec and use Forge's original config system for a NeoForge config.