Write a list of bytes to a file.
Opens the file, writes the list of bytes to it, and closes the file.
Returns a Future<File> that completes with this File object once
the entire operation has completed.
By default writeAsBytes creates the file for writing and truncates the file if it already exists. In order to append the bytes to an existing file, pass FileMode.APPEND as the optional mode parameter.
If the argument flush is set to true, the data written will be
flushed to the file system before the returned future completes.
Source
Future<File> writeAsBytes(List<int> bytes,
{FileMode mode: FileMode.WRITE, bool flush: false});