imghdr module has a cli that can display the image type for a given filename and also recurse through directories. I would like to propose following changes :

* Add tests for the imghdr cli.
* The cli uses hardcoded '/' separator in the end for directories this is a minor issue with windows where the separators are \ and the last separator is displayed with / like c:\Foo\Bar\Spam/ . Using os.sep can be a better option here.

I have a PR that I will add shortly for review.