Add a download() function into the RepoAPI object

[kbolashev]

RepoAPI should have a download() function that utilizes the common.download.download_files() function to download the whole repo or a directory in a repo in a parallelized fashion.

repo = RepoAPI("user/repo")
repo.download(outdir="/home/user/my-repo")
# OR
repo.download("data/images", "/home/user/images")

Probably should be recursive by default with the ability to turn it off

[itssiddhantjain]

Hello @kbolashev , please assign this issue to me as I have already worked on this kind of problem in past and has a great experience.

[kbolashev]

@itssiddhantjain Feel free to make a PR for whatever issue you want to tackle 👍