Merge pull request #2589 from davidsh/update_readme

Update README.md for System.Net.Primitives

Author: stephentoub

README.md

@@ -93,6 +93,7 @@ More libraries are coming soon (the overall list of items we currently plan to m
 |<sub>**System.Linq.Queryable**<br/>[![MyGet Package](https://img.shields.io/myget/dotnet-core/v/System.Linq.Queryable.svg)](https://www.myget.org/gallery/dotnet-core)</sub>|<sub>Provides LINQ standard query operators that operate on objects that implement ```IQueryable<T>```.</sub>|
 |<sub>**System.Net.Http**<br/>[![MyGet Package](https://img.shields.io/myget/dotnet-core/v/System.Net.Http.svg)](https://www.myget.org/gallery/dotnet-core)</sub>|<sub>Provides a programming interface for modern HTTP applications, including HTTP client components that allow applications to consume web services over HTTP and HTTP components that can be used by both clients and servers for parsing HTTP headers.</sub>|
 |<sub>**System.Net.Http.WinHttpHandler**<br/>[![MyGet Package](https://img.shields.io/myget/dotnet-core/v/System.Net.Http.WinHttpHandler.svg)](https://www.myget.org/gallery/dotnet-core)</sub>|<sub>Provides a message handler for HttpClient based on the WinHTTP interface of Windows. While similar to HttpClientHandler, it provides developers more granular control over the application's HTTP communication than the HttpClientHandler.</sub>|
+|<sub>**System.Net.Primitives**<br/>[![MyGet Package](https://img.shields.io/myget/dotnet-core/v/System.Net.Primitives.svg)](https://www.myget.org/gallery/dotnet-core)</sub>|<sub>Provides common types for network-based libraries, including System.Net.IPAddress, System.Net.IPEndPoint, and System.Net.CookieContainer.</sub>|
 |<sub>**System.Net.Requests**<br/>[![MyGet Package](https://img.shields.io/myget/dotnet-core/v/System.Net.Requests.svg)](https://www.myget.org/gallery/dotnet-core)</sub>|<sub>Provides older classes (such as HttpWebRequest and HttpWebResponse) for sending HTTP requests and receiving HTTP responses from a resource identified by a URI. _This library is available primarily for compatibility; developers should prefer the classes in the System.Net.Http package._</sub>|
 |<sub>**System.Net.WebHeaderCollection**<br/>[![MyGet Package](https://img.shields.io/myget/dotnet-core/v/System.Net.WebHeaderCollection.svg)](https://www.myget.org/gallery/dotnet-core)</sub>|<sub>Contains types that represent HTTP request and response headers. This library is used with classes such as System.Net.HttpWebRequest and System.Net.HttpWebResponse and allows developers to query/edit header names/values.</sub>|
 |<sub>**System.Net.WebSockets**<br/>[![MyGet Package](https://img.shields.io/myget/dotnet-core/v/System.Net.WebSockets.svg)](https://www.myget.org/gallery/dotnet-core)</sub>|<sub>Provides the System.Net.WebSockets.WebSocket abstract class and related types to allow developers to implement the WebSocket protocol (RFC 6455). WebSockets provide full-duplex communication over a single TCP connection.</sub>|