• Redefined the Reader and Writer interface apis in
  pkg/geoipupdate/database. This change aims to to make it easier to
  introduce custom implementations of these interfaces.
• Changed the signature of NewConfig in pkg/geoipupdate to accept
  optional parameters. This change allows the introduction of new
  flags or config options without making breaking changes to the function's
  signature.
• Introduced Parallelism as a new flag and config option to enable
  concurrent database updates.