Add powershell detection

[miah]

Fixes: #518

[chef-expeditor]

Hello miah! Thanks for the pull request!

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   a. If everything looks good, one of them will approve it, and your PR will be merged.
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Thank you for contributing!

[zenspider]

WHERE IS THE POWERSHELL TEST?!?!?

😛

[codeclimate]

Code Climate has analyzed commit a4db189 and detected 6 issues on this pull request.

Here's the issue category breakdown:

Category	Count
Complexity	2
Style	4

View more on Code Climate.

[zenspider]

already approved since we paired. 😛