Ominous item spawners should show their item in the tooltip

[haykam821]

Enhancement

Item frame tooltips get replaced with the held item's name and icon, so ominous item spawners should act the same way.

To spawn an ominous item spawner with an item in it, run this command:

/summon minecraft:ominous_item_spawner ~ ~ ~ {item: {id: "minecraft:stone"}, spawn_item_after_ticks: 3000}