Add ART library to UIExplorer for iOS, with sample and snapshot test

Summary:
**Motivation**

The ART library is part of the react-native repo, but is not included in UIExplorer and has no native testing.  This PR adds the ART library to UIExplorer, adds an example tab for it, and adds a snapshot test.

**Test plan**

New snapshot test.
Closes https://github.com/facebook/react-native/pull/13621

Differential Revision: D4954082

Pulled By: javache

fbshipit-source-id: 83e21c5df1b766ff6ca9f8914eb3382f7323627d

RNTester/js/ARTExample.js

@@ -0,0 +1,104 @@
+/**
+ * Copyright (c) 2013-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * The examples provided by Facebook are for non-commercial testing and
+ * evaluation purposes only.
+ *
+ * Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON INFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * @flow
+ * @providesModule ARTExample
+ */
+'use strict';
+
+var React = require('react');
+var ReactNative = require('react-native');
+var {
+  ART,
+  Platform,
+  View,
+} = ReactNative;
+
+const {
+  Surface,
+  Path,
+  Group,
+  Transform,
+  Shape,
+} = ART;
+
+
+var scale = Platform.isTVOS ? 4 : 1;
+
+class ARTExample extends React.Component{
+    render(){
+        const pathRect = new Path()
+            .moveTo(scale * 0,scale * 0)
+            .lineTo(scale * 0,scale * 110)
+            .lineTo(scale * 110,scale * 110)
+            .lineTo(scale * 110,scale * 0)
+            .close();
+
+        const pathCircle0 = new Path()
+            .moveTo(scale * 30,scale * 5)
+            .arc(scale * 0,scale * 50,scale * 25)
+            .arc(scale * 0,-scale * 50,scale * 25)
+            .close();
+
+        const pathCircle1 = new Path()
+            .moveTo(scale * 30,scale * 55)
+            .arc(scale * 0,scale * 50,scale * 25)
+            .arc(scale * 0,-scale * 50,scale * 25)
+            .close();
+
+        const pathCircle2 = new Path()
+            .moveTo(scale * 55,scale * 30)
+            .arc(scale * 50,scale * 0,scale * 25)
+            .arc(-scale * 50,scale * 0,scale * 25)
+            .close();
+
+        const pathCircle3 = new Path()
+            .moveTo(scale * 55,scale * 80)
+            .arc(scale * 50,scale * 0,scale * 25)
+            .arc(-scale * 50,scale * 0,scale * 25)
+            .close();
+
+        return (
+            <View>
+                <Surface width={scale * 200} height={scale * 200}>
+                    <Group>
+                        <Shape d={pathRect} stroke="#000080" fill="#000080" strokeWidth={scale}/>
+                        <Shape d={pathCircle0} stroke="#FF0000" fill="#FF0000" strokeWidth={scale}/>
+                        <Shape d={pathCircle1} stroke="#00FF00" fill="#00FF00" strokeWidth={scale}/>
+                        <Shape d={pathCircle2} stroke="#00FFFF" fill="#00FFFF" strokeWidth={scale}/>
+                        <Shape d={pathCircle3} stroke="#FFFFFF" fill="#FFFFFF" strokeWidth={scale}/>
+                    </Group>
+                </Surface>
+            </View>
+        );
+    }
+}
+
+exports.title = '<ART>';
+exports.displayName = 'ARTExample';
+exports.description = 'ART input for numeric values';
+exports.examples = [
+  {
+    title: 'ART Example',
+    render(): React.Element<any> {
+      return <ARTExample />;
+    }
+  },
+];