I am trying to implement a nether pouch using the nether-chest mod. The idea is an end pouch but with the nether-chest opening.

I am currently trying to extend all the classes but as I am having difficulty with this so my second pass is to just get it working by forking the Things mod and adding new code.

I noticed when following downloading the repo that the ThingsConfig file is missing and that without it, I cannot compile and run minecraft.

please update the Repo to include the ThingsConfig

You are misunderstanding how Things config works. It is a part of owo-config (owo-lib). It is driven by an annotation processor, and the configuration code is generated at build/compile time. Some details on the usage is described here: https://docs.wispforest.io/owo/config/getting-started/

If you have owo-lib declared in your build.gradle file then you want to enable the annotation processor as described

dependencies {
    annotationProcessor modImplementation("io.wispforest:owo-lib:${project.owo_version}")
}

If you are just including Things alone then I am unsure on how you want to properly build against it. It might be enough to just use annotationProcessor and modCompileOnly in the buildscript instead, like so:

dependencies {
    annotationProcessor modCompileOnly("io.wispforest:owo-lib:${project.owo_version}")
}

That way the code might generate correctly, and you would not need to include owo in any way.

Given that this issue seems to stem from your lack of familiarity with owo-config (as pointed out by Noaaan), I'll close this as Not Planned for now

Cheers