PLYMOUTH — It’s that time of the year again — Plymouth Alive’s 21st Kielbasa Festival gets underway at 11 a.m. Friday, and Main Street will be packed with 108 vendors and thousands of people. The two-day festival runs through Saturday in downtown Plymouth. If you don’t know how to get there, just follow the aroma of garlic. If you like Polish cuisine, the Kielbasa Festival will have plenty of…