ansiSgr method Null safety

Chalk ansiSgr(
  1. dynamic openCode,
  2. dynamic closeCode
)

https://en.wikipedia.org/wiki/ANSI_escape_code

Implementation

Chalk ansiSgr(dynamic openCode, dynamic closeCode) {
  // We use _ansiSGRModiferOpen() for both because we dont want
  // useFullResetToClose to affect THESE USER specified open/close SGR's
  return _createStyler(
      _ansiSGRModiferOpen(openCode), _ansiSGRModiferOpen(closeCode), this);
}