Addition of a requirements file

[sbhark]

Hi there,

I was in the process of installing a new Windows agent for a private WPT instance. I followed the install guide here: https://github.com/WPO-Foundation/wptagent/blob/master/docs/install.md. The script works great! Thank you.

I do have a small of suggestion of adding a requirements file to install the dependencies required by the script. I did have to install requests and pypiwin32 to for a successful execution.

It wasn't a big deal but having a requirements file to install anything needed by the script beforehand is definitely a nice to have 😄

Thanks!