Add a SlimefunItem constructor that only needs `ItemGroup` and `SlimefunItemStack`

[ProfElements]

Description

I have a seperate system of managing recipes and would like a shorthand to not have to define them at item creation time.

Proposed changes

Add a SlimefunItem constructor that just passed RecipeType.NULL and empty recipe for its recipe and input fields.

Related Issues (if applicable)

Checklist

• [ ] I have fully tested the proposed changes and promise that they will not break everything into chaos.
• [ ] I have also tested the proposed changes in combination with various popular addons and can confirm my changes do not break them.
• [ ] I have made sure that the proposed changes do not break compatibility across the supported Minecraft versions (1.16.* - 1.20.*).
• [ ] I followed the existing code standards and didn't mess up the formatting.
• [ ] I did my best to add documentation to any public classes or methods I added.
• [ ] I have added Nonnull and Nullable annotations to my methods to indicate their behaviour for null values
• [ ] I added sufficient Unit Tests to cover my code.

[github-actions[bot]]

Pro Tip! You can help us label your Pull Requests by using the following branch naming convention next time you create a pull request. ❤️

Branch naming convention	Label
feature/**	🎈 Feature
fix/**	✨ Fix
chore/**	🧹 Chores
api/**	🔧 API
performance/**	💡 Performance Optimization
compatibility/**	🤝 Compatibility

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[github-actions[bot]]

Slimefun preview build

A Slimefun preview build is available for testing! Commit: 8430677f

https://preview-builds.walshy.dev/download/Slimefun/4179/8430677f

Note: This is not a supported build and is only here for the purposes of testing. Do not run this on a live server and do not report bugs anywhere but this PR!