Support third party modules

[ThomasNieto]

Summary of the new feature / enhancement

I would like this module to support third party modules so I can publish what's new content for my module and users can use this module to retrieve it.

Get-WhatsNew -Module MyModule

Proposed technical implementation details (optional)

A module would need to indicate that it supports this feature and ideally pull the content from a url. The easiest way I can think of is adding a module manifest key in PrivateData section with the url.

PrivateData = @{ WhatsNewUri = 'https://mywebsite.com/whatsnew' }