Growing crops on rooted dirt increases speed of growing

Rooted dirt is a rare dirt variant. It is currently a purely decorative block, associated with nutrients and nature. Either placing a tilled block on top or tilling rooted dirt should give faster growing speeds for crops planted in the till (1.5x-2x). This would give players reasons to gather rooted dirt (rather than it just being for hanging roots) and it would give players ways to upgrade their farms and crops.