For many, June is the official, first month of summer, but that’s not the only thing worth celebrating. There are tons of other, awesome, wacky holidays, and what better way to observe them than with some cheap custom tee shirts? Here are just a few super neat holidays coming up worthy of having their own custom tees! National Doughnut Day. National Doughnut Day is celebrated the first Friday of June, so it’s coming fast. Dunkin’ Donuts is even giving away a free doughnut to celebrate. Making a custom tee for this day, in particular, is a great idea, so that…