Design decision regarding nflfastR::calculate_stats() required

[mrcaseb]

nflfastR::calculate_stats() is the new approach regarding stats of any type. It's list of arguments is as follows:

seasons = nflreadr::most_recent_season(),
summary_level = c("season", "week"),
stat_type = c("player", "team"),
season_type = c("REG", "POST", "REG+POST")

We need to decide how we would like to handle the outputs and whether or not it should be a new function.