Add completion for PowerShell

[manchoz]

Add support to generate PowerShell completions for arduino-cli in PowerShell 5.0+

This PR:

• Add PowerShell to completion code generation

While waiting for documentation, please, you can test it following the instructions at Autocomplete in PowerShell.

[manchoz]

Add tests and documentation.

@umbynos @per1234 please, review.

Let me know if I need to squash the commits.

[silvanocerza]

Just tested and it works great, I think there's only need for that small docs edit and then it's good to go for me.

[silvanocerza]

Let me know if I need to squash the commits.

No worries, it will be squashed when merged.