Add a requirement info

[Rajbir98]

Add the requirement of windows PowerShell 5 for lower version of windows

[Daksh777]

By default, Windows 7 comes with PowerShell version 2.0 installed.
The simplest solution is to upgrade your version of PowerShell to version 5.1.
You can do that by downloading the Windows Management Framework: https://www.microsoft.com/en-us/download/details.aspx?id=54616

I'll add the requirement and a note in the README. Thank you for the reminder.