Added a method to create a Mek Module Item.

This is a simple example in kjs

const $Rarity = Java.loadClass("net.minecraft.world.item.Rarity")
StartupEvents.registry("item", (event) => {
    const a = event.create(
        "module_create_energy_unit", "mek_unit"
    )
    
    // === MekUnitItemBuilder ===
    
    a.setSlot("all")
    a.tickServer((modlue, player) => {
        const maxEnergy = KJSModuleUtils.getMaxEnergy(modlue.getContainer())
        modlue.getEnergyContainer().setEnergy(maxEnergy)
    })
    
    // === ItemBuilder ===

    a.glow(true)
    a.rarity($Rarity.EPIC);
})