Returns a data frame of all currently injured players for a selected league
     
    
    Usage
    tm_league_injuries(country_name, league_url = NA)
 
    
    Arguments
- country_name
- the country of the league's players 
- league_url
- league url from transfermarkt.com. To be used when country_name not available in main function 
 
    
    Value
    returns a dataframe of injured players in the selected league