The fintech has delivered 21% annual returns since its IPO in 2015. Can it continue to deliver?Block (SQ 0.15%) is at the forefront of the digital payments revolution and has gained 420%, or 21%, compounded annually since its public debut. With digital payments expected to explode, does Block have what it takes to make you a millionaire? Let's dive in and find out.To be a millionaire maker, a stock must deliver incredible results over a long period. For example, if you start with an initial investment of $1 ...