Returns the URLs for all teams for a given league season
tm_league_team_urls(country_name, start_year, league_url = NA)the country of the league's players
the start year of the season (2020 for the 20/21 season)
league url from transfermarkt.com. To be used when country_name not avalilable in main function
returns a character vector of all transfermarkt team URLs for a selected league