Nether bricks and iron and gold nuggets can be used as fuel in furnaces

Summary:
The nether brick item can be used as fuel in furnaces. Iron nuggets and gold nuggets can also be used. All of them burn for 20 ticks in a furnace or 10 ticks in a blast furnace or smoker.

Steps to Reproduce:

1. Obtain nether brick and a smeltable item
2. Place and open a furnace
3. Place the nether brick in the bottom slot and the smeltable item in the top slot

Observed Results:
The item starts smelting.

Expected Results:
Nether brick should not be able to be placed in the bottom slot of a furnace.

Screenshot: