Show tooltip with descriptive item name when switching slots

[deathcap]

When the player changes the active slot selection, briefly show a tooltip containing the item name. This would be useful to help teach players what the items are via their icon, easier than opening voxel-inventory-dialog and mousing over the inventory-window.

Similar purpose to https://github.com/deathcap/voxel-voila but for inventory items instead of in-world blocks