Returns all people who have held the selected role in a team's history
tm_team_staff_history(team_urls, staff_role = "Manager")transfermarkt.com team(s) url for a season
the role description which can be found here: https://github.com/JaseZiv/worldfootballR_data/blob/master/raw-data/transfermarkt_staff/tm_staff_types.csv
returns a data frame of all selected staff roles for a team(s) history