Support for {path = "foo.whl"}

[adimajo]

Hi & thanks for the amazing job on this tool.
I have in my Pipfile some dependencies to local wheels, e.g. :
pycld2 = {path = "./windows_wheels/pycld2-0.41-cp37-cp37m-win_amd64.whl"}
which, if you wondered, comes from a bug in package polyglot on windows (see aboSamoor/polyglot#91).

This is currently being translated by pipenv-to-requirements in requirements.txt as:
pycld2==0.41
which is kind of incorrect since it simply won't install on my Windows machine.
I saw issue #1 but it seems like this is a local package (with all its source files, etc.) whereas I'm dealing with a wheel, so I guess it's handled a bit differently. Any idea how to achieve what I'm looking for?