Adding a requirements.txt

Hi Adnan 👋

I would suggest to add a requirements.txt, `touch requirements.txt && pip freeze > requirements.txt`, for easier reproduction where one can use the package with the same version as you did. I haven't had an issue yet, but once a package gets updated, it could make debugging and version guessing more difficult 😉

Great work as always! ✌️

All the best, 
Dietrich