create abstract method
- {bool recursive = false}
Creates the directory if it doesn't exist.
If recursive is false, only the last directory in the path is
created. If recursive is true, all non-existing path components
are created. If the directory already exists nothing is done.
Returns a Future<Directory> that completes with this
directory once it has been created. If the directory cannot be
created the future completes with an exception.
Implementation
Future<Directory> create({bool recursive = false});