Should also support cached downloading for gdrive folders about gdown

[wkentaro]

@rautnikhil Something like below?

download_folder(
    url,
    ...
    md5={
       "textfile.txt": "xxxxxxxxx",
       "dir1/textfile2.txt": "yyyyyyyyyyyyyy",
    }
)

[rautnikhil]

Hi @wkentaro ,
I am proposing following solution for non md5 based verification; that is skip the download if file already exist at the download destination by just checking existence of file path like "if osp.exists(path)".
However for md5 based verification something like above can be implemented.

#code snippet for further reference

def download_folder(
url=None,
id=None,
output=None,
quiet=False,
proxy=None,
speed=None,
use_cookies=True,
remaining_ok=False,
exist_ok=False #New parameter
)
.
.

filenames = []
for file_id, file_path in directory_structure:
    if file_id is None:  # folder
        if not osp.exists(file_path):
            os.makedirs(file_path)
        continue

   if exist_ok:
        filename = cached_download(
            url="https://drive.google.com/uc?id=" + file_id,
            output=file_path,
            quiet=quiet,
            postprocess=None
        )
  else
       filename = download(
        "https://drive.google.com/uc?id=" + file_id,
        output=file_path,
        quiet=quiet,
        proxy=proxy,
        speed=speed,
        use_cookies=use_cookies,
    )