ras_id and otc_id need to be added to nflreadr::load_ff_playerids()

[TheMathNinja]

I noticed that ras_id and otc_id live as variables in the missing_ids.csv file here on dynastyprocess, but are not currently variables in nflreadr::load_ff_playerids(). This file and the function it feeds should mirror each other, yes? Looks like the csv has useful data for the function.