Windows percentage based threshold

[gitgryphon]

Description
Add the ability to use a percentage based threshold on windows like already exists for linux
docuum --threshold '50%'

Additional considerations
#216 (review) - mentioned it could be more difficult to setup on windows, as docker can be run in a vm on windows, but typically it's just run as a service. Running those commands in that comment:

PS C:\Users\me>  docker info --format '{{.DockerRootDir}}'
C:\docker\data
PS C:\Users\me> dir C:\docker\data
<Some dir output>

The directory exists, so the disk size method could work for instances where docker is a service, and not running in a vm. For validaton we could add a check to see if the disk checks works or if docker is running in a VM, and then throw a helpful error, otherwise use similar logic to the linux method

[stepchowfun]

That sounds reasonable to me! I'd be happy to review a PR if anyone can contribute it.