Add support to set the asset root used for asset downloads explicitly.

[shartte]

The use cases I see:

• Setting NFRT_ASSET_ROOT via Github Action to use a cache directory that is cross-branch, since the MC assets do not change that much from version to version.
• Setting NFRT_ASSET_REPOSITORY for people that want to use a local proxy (we might also use a pull-through HTTP proxy for assets).

[neoforged-pr-publishing]

• Publish PR to GitHub Packages

Last commit published: 62b609e65fa83d066935f79505b99c308a6ac3f3.

PR Publishing

The artifacts published by this PR:

• 📦 net.neoforged:neoform-runtime:1.0.19-pr-56-fixed-asset-root

Repository Declaration

In order to use the artifacts published by the PR, add the following repository to your buildscript:

repositories {
    maven {
        name 'Maven for PR #56' // https://github.com/neoforged/NeoFormRuntime/pull/56
        url 'https://prmaven.neoforged.net/NeoFormRuntime/pr56'
        content {
            includeModule('net.neoforged', 'neoform-runtime')
        }
    }
}

[neoforged-releases]

🚀 This PR has been released as NeoFormRuntime version 1.0.19.