Product roadmap (#5127)

* first draft

* add languages

* more content

* add some missing areas

* add spark

* add interactive

* Update F# 5 list for product roadmap (#5131)

* small changes

* Added CLI/SDK and Visual Basic sections

* Fixed bad formatting for CLI/SDK

* fix legend

* clean up text

* Add ML.NET

* add tye

* add winforms

* Update current.md

* Update current.md

* Update current.md

* Update current.md

* Update current.md

* Add gRPC

* More gRPC

* Remove required component parameters from Blazor roadmap

* table changes + wpf

* move table up

* Update current.md (#5144)

Xamarin roadmap work through end of 2020

* wpf updates

* Update current.md

* Update current.md

Co-authored-by: Phillip Carter <pcarter@fastmail.com>
Co-authored-by: Kathleen Dollard <kdollard@microsoft.com>
Co-authored-by: Jamshed Damkewala <jamshedd@users.noreply.github.com>
Co-authored-by: Sourabh Shirhatti <shirhatti@outlook.com>
Co-authored-by: Daniel Roth <daroth@microsoft.com>
Co-authored-by: David Ortinau <david.ortinau@microsoft.com>

README.md

@@ -33,6 +33,8 @@ The latest major release is [.NET Core 3.1](release-notes/3.1). The latest patch
 
 The .NET Core team encourages [contributions](https://github.com/dotnet/runtime/blob/master/CONTRIBUTING.md), both issues and PRs. The first step is finding the [.NET Core repository](Documentation/core-repos.md) that you want to contribute to.
 
+Check the [product roadmap](https://aka.ms/dotnet-product-roadmap) to see what the team is focusing on.
+
 ### Community
 
 This project uses the [.NET Foundation Code of Conduct](https://dotnetfoundation.org/code-of-conduct) to define expected conduct in our community.