Initial WPF Support (#385)

* initial support for WPF

* update readme with WPF specific instructions

* remove autogenerated .gitattributes file

* reference RNW NPM package instead of hard-coded local reference

windows/ReactNativeVideo.Net46/ReactVideoPackage.cs

@@ -0,0 +1,30 @@
+using ReactNative.Bridge;
+using ReactNative.Modules.Core;
+using ReactNative.UIManager;
+using System;
+using System.Collections.Generic;
+
+namespace ReactNativeVideo
+{
+    public class ReactVideoPackage : IReactPackage
+    {
+        public IReadOnlyList<Type> CreateJavaScriptModulesConfig()
+        {
+            return Array.Empty<Type>();
+        }
+
+        public IReadOnlyList<INativeModule> CreateNativeModules(ReactContext reactContext)
+        {
+            return Array.Empty<INativeModule>();
+
+        }
+
+        public IReadOnlyList<IViewManager> CreateViewManagers(ReactContext reactContext)
+        {
+            return new List<IViewManager>
+            {
+                new ReactVideoViewManager(),
+            };
+        }
+    }
+}