addFileSync method
Implementation
void addFileSync(File file, [String? filename, int? level]) {
final fileStream = InputFileStream(file.path);
final archiveFile =
ArchiveFile.stream(filename ?? path.basename(file.path), fileStream);
archiveFile.lastModTime =
(file.lastModifiedSync()).millisecondsSinceEpoch ~/ 1000;
archiveFile.mode = (file.statSync()).mode;
_encoder.add(archiveFile, level: level);
}