Add installation file for windows users

[birgits]

Some packages cause problems when installed using pip on Windows. In order to make usage of the windpowerlib easier for Windows users we should provide a yml file where those packages are installed using conda and add installation instructions for it.

[p-snft]

I allowed myself to add a comment to the readme, so that Windows users do not try to just pip install feedinlib: https://github.com/oemof/feedinlib/commit/773cde0a2e5662b37d3be12d4d4ef6084907f5e6