Option to use github login as display name

[Fasjeit]

• New option preferLogin: when set makes svg use github login instead of name (default is false).

  ?user=brunobritodev&cardType=level&theme=default&showIcons=true&preferLogin=false&properties=Background

  

• If gihub user name is null or empty - use login instead

  var displayName = (string.IsNullOrEmpty(rank.UserStats.Name) || (_options.PreferLogin ?? false)) 
  ? rank.UserStats.Login.Truncate(25)
  : rank.UserStats.Name.Truncate(25);

  

ps. I don't know why rings are "rotated" that way in screenshots in my test build...

fixes #24