Add 'thirdPartyCookiesEnabled' prop on WebView to enable third party …

Summary:
…cookies on Android Lollipop or later versions.

Third party cookies in WebView are [disabled by default](https://developer.android.com/reference/android/webkit/CookieManager.html#setAcceptFileSchemeCookies(boolean)) on Android Lollipop or later versions. This prevented users from logging in by using _Login by Facebook_ method (in redirect mode) in Android Webview.

This PR exposes a prop `thirdPartyCookiesEnabled` which will enable third party cookies in Android Webview. This setting is ignored on versions below Android Lollipop and on iOS as third party cookies are enabled in them by default.

Appropriate documentation was added in code and they were reflected in the website.
Closes https://github.com/facebook/react-native/pull/14013

Differential Revision: D5145059

Pulled By: shergin

fbshipit-source-id: 67bcb3a497a9c6f6db1d12e8d16197d2facd157e

ReactAndroid/src/main/java/com/facebook/react/views/webview/ReactWebViewManager.java

@@ -32,6 +32,7 @@ import android.webkit.WebViewClient;
 import android.webkit.JavascriptInterface;
 import android.webkit.ValueCallback;
 import android.webkit.WebSettings;
+import android.webkit.CookieManager;
 
 import com.facebook.common.logging.FLog;
 import com.facebook.react.common.ReactConstants;
@@ -370,6 +371,13 @@ public class ReactWebViewManager extends SimpleViewManager<WebView> {
     view.getSettings().setJavaScriptEnabled(enabled);
   }
 
+  @ReactProp(name = "thirdPartyCookiesEnabled")
+  public void setThirdPartyCookiesEnabled(WebView view, boolean enabled) {
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+      CookieManager.getInstance().setAcceptThirdPartyCookies(view, enabled);
+    }
+  }
+
   @ReactProp(name = "scalesPageToFit")
   public void setScalesPageToFit(WebView view, boolean enabled) {
     view.getSettings().setUseWideViewPort(!enabled);