Canadian cannabis group Sundial Growers (NASDAQ:SNDL) stock has been one of the top-performing names so far in 2021. Source: Jetacom Autofocus / Shutterstock.com SNDL stock is up about 90% year-to-date (YTD). By comparison, the ETFMG Alternative Harvest ETF (NYSEARCA:MJ) is up 34%. SNDL shares began the year around 50 cents. Then, in February they saw a…