Markdown based documentation for packages

[anangaur]

Announcing support for rich markdown based documentation for packages

This feature has following parts:
1. Ability to associate a markdown documentation to packages (and existing packages)
2. Understand markdown and render it properly on NuGet.org package details page
3. Ability to associate markdown documentation content while packing the package, from clients
4. Ability on VS client to show this markdown content.

1 and 2 have been implemented as part of 2017 Interns project and released now. Please provide your feedback on the feature - both implemented and pending parts.

Spec wiki	Discussion issue
https://github.com/NuGet/Home/wiki/Package-README.md-support	NuGet/NuGetGallery#2280

In order to put markdown documentation, you can edit an existing package and add the required documentation:

This will appear as below: