Split out 'socket' hosting model into a separate optional NuGet package, since most developers won't need it

src/Microsoft.AspNetCore.NodeServices.Sockets/SocketNodeServicesOptionsExtensions.cs

@@ -0,0 +1,21 @@
+using System;
+
+namespace Microsoft.AspNetCore.NodeServices.Sockets
+{
+    /// <summary>
+    /// Extension methods that help with populating a <see cref="NodeServicesOptions"/> object.
+    /// </summary>
+    public static class NodeServicesOptionsExtensions
+    {
+        /// <summary>
+        /// Configures the <see cref="INodeServices"/> service so that it will use out-of-process
+        /// Node.js instances and perform RPC calls over binary sockets (on Windows, this is
+        /// implemented as named pipes; on other platforms it uses domain sockets).
+        /// </summary>
+        public static void UseSocketHosting(this NodeServicesOptions options)
+        {
+            var pipeName = "pni-" + Guid.NewGuid().ToString("D"); // Arbitrary non-clashing string
+            options.NodeInstanceFactory = () => new SocketNodeInstance(options, pipeName);
+        }
+    }
+}