Add PayNow NeoForge mod setup

[Adammatthiesen]

This pull request introduces a new module, paynow-neoforge, adding support for the NeoForge modding platform to the PayNow Minecraft integration. The changes include the full setup for building, configuring, and running the NeoForge mod, as well as registering it in the project and documentation. The most important changes are grouped below:

NeoForge Module Addition:

• Added the new paynow-neoforge module, including its source code, build configuration, and resources. This module implements PayNow integration for NeoForge servers, handling server events, player joins, command registration, and configuration management. (paynow-neoforge/src/main/java/gg/paynow/paynowneoforge/PayNowNeoForge.java, paynow-neoforge/src/main/java/gg/paynow/paynowneoforge/PayNowNeoForgeCommand.java) [1] [2]
• Created a build.gradle for the paynow-neoforge module, specifying dependencies, plugin setup, Java version, resource processing, shadow jar configuration, and publishing settings. (paynow-neoforge/build.gradle)
• Added gradle.properties for the paynow-neoforge module, defining mod, environment, and build properties such as mod ID, name, license, and Minecraft/NeoForge versions. (paynow-neoforge/gradle.properties)
• Included a NeoForge mod descriptor file, neoforge.mods.toml, with metadata, dependencies, and description for the new mod. (paynow-neoforge/src/main/resources/META-INF/neoforge.mods.toml)

Project Configuration & Documentation:

• Registered the new module in the project settings and added the NeoForge Maven repository for plugin management. (settings.gradle) [1] [2]
• Updated the README.md to include a reference to the new paynow-neoforge module. (README.md)

PR Description made with the aid of Github's Summary AI

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Tested using a NeoForge 1.21.1 server that has now been successfully linked to Paynow!