Tag implication: onigiri -> food

onigiri should imply food, but doesn't yet.

There are a *huge* number of food items that are not implied as food yet. The best bet is to either manually type the food tag or use a much more common food tag alongside the onigiri tag, in this case rice, and hope that has the implication.

rice is either for a bowl of rice or individual grains. Let's not start implicating everything to everything out of laziness.

Done