Support windows paths for cache

[scivision]

Using the same Github personal token for Linux (windows subsystem for linux) and windows on the same PC, the astronomer linux Go-based executable works fine, but the Windows Go-based executable gives an error like:

astronomer.exe username/repo

Beginning fetching process for repository username/repo
Pre-fetching all stargazers...ko
✖ failed to query stargazer data: unable to write user contribution data to cache: 
unable to create cache file: open data\username\repo\https-api-github-com-graphql-list-firstpage: 
The system cannot find the path specified.

[Ullaakut]

Hi @scivision and thanks for reporting this bug! 👍