Dragon Con is set to give Atlanta's top mentors a financial boost as part of its annual philanthropic push. The internationally known pop-culture convention picked Big Brothers Big Sisters of Metro Atlanta as its official charity for 2020. Officials with the five-day event have raised more than $566,000 over the past five years for its annual official charities through auctions, merchandise sales, events and an up to $100,000 match. Last year’s charity, The American Heart Association, received…