Add example on Components

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Adding example on components section with [react-native-web-player](https://github.com/dabbott/react-native-web-player)

- ActivityIndicator
- TouchableOpacity
- TouchableHighlight

Screenshot on http://localhost:8079/react-native/docs/activityindicator.html
![react-native-activityindicator](https://user-images.githubusercontent.com/13135332/30432801-adca0982-9988-11e7-8e70-94ad9e42ea43.png)

Screenshot on http://localhost:8079/react-native/docs/touchableopacity.html
![react-native-touchableopacity](https://user-images.githubusercontent.com/13135332/30432718-80570554-9988-11e7-9c81-15ab98327fed.png)

Screenshot on http://localhost:8079/react-native/docs/touchablehighlight.html
![react-native-touchablehighlight](https://user-images.githubusercontent.com/13135332/30432733-8290fbb8-9988-11e7-94a1-86c3166e544d.png)
Closes https://github.com/facebook/react-native/pull/15950

Differential Revision: D5881366

Pulled By: hramos

fbshipit-source-id: 2926071723defedf9ed5cb1b1128204256c71dd9

Libraries/Components/ActivityIndicator/ActivityIndicator.js

@@ -36,6 +36,46 @@ type DefaultProps = {
 
 /**
  * Displays a circular loading indicator.
+ *
+ * ### Example
+ *
+ * ```ReactNativeWebPlayer
+ * import React, { Component } from 'react'
+ * import {
+ *   ActivityIndicator,
+ *   AppRegistry,
+ *   StyleSheet,
+ *   Text,
+ *   View,
+ * } from 'react-native'
+ *
+ * class App extends Component {
+ *   render() {
+ *     return (
+ *       <View style={[styles.container, styles.horizontal]}>
+ *         <ActivityIndicator size="large" color="#0000ff" />
+ *         <ActivityIndicator size="small" color="#00ff00" />
+ *         <ActivityIndicator size="large" color="#0000ff" />
+ *         <ActivityIndicator size="small" color="#00ff00" />
+ *       </View>
+ *     )
+ *   }
+ * }
+ *
+ * const styles = StyleSheet.create({
+ *   container: {
+ *     flex: 1,
+ *     justifyContent: 'center'
+ *   },
+ *   horizontal: {
+ *     flexDirection: 'row',
+ *     justifyContent: 'space-around',
+ *     padding: 10
+ *   }
+ * })
+ *
+ * AppRegistry.registerComponent('App', () => App)
+ * ```
  */
 /* $FlowFixMe(>=0.53.0 site=react_native_fb,react_native_oss) This comment
  * suppresses an error when upgrading Flow's support for React. To see the

Libraries/Components/Touchable/TouchableHighlight.js

@@ -71,6 +71,74 @@ const PRESS_RETENTION_OFFSET = {top: 20, left: 20, right: 20, bottom: 30};
  *   );
  * },
  * ```
+ *
+ *
+ * ### Example
+ *
+ * ```ReactNativeWebPlayer
+ * import React, { Component } from 'react'
+ * import {
+ *   AppRegistry,
+ *   StyleSheet,
+ *   TouchableHighlight,
+ *   Text,
+ *   View,
+ * } from 'react-native'
+ *
+ * class App extends Component {
+ *   constructor(props) {
+ *     super(props)
+ *     this.state = { count: 0 }
+ *   }
+ *
+ *   onPress = () => {
+ *     this.setState({
+ *       count: this.state.count+1
+ *     })
+ *   }
+ *
+ *  render() {
+ *     return (
+ *       <View style={styles.container}>
+ *         <TouchableHighlight
+ *          style={styles.button}
+ *          onPress={this.onPress}
+ *         >
+ *          <Text> Touch Here </Text>
+ *         </TouchableHighlight>
+ *         <View style={[styles.countContainer]}>
+ *           <Text style={[styles.countText]}>
+ *             { this.state.count !== 0 ? this.state.count: null}
+ *           </Text>
+ *         </View>
+ *       </View>
+ *     )
+ *   }
+ * }
+ *
+ * const styles = StyleSheet.create({
+ *   container: {
+ *     flex: 1,
+ *     justifyContent: 'center',
+ *     paddingHorizontal: 10
+ *   },
+ *   button: {
+ *     alignItems: 'center',
+ *     backgroundColor: '#DDDDDD',
+ *     padding: 10
+ *   },
+ *   countContainer: {
+ *     alignItems: 'center',
+ *     padding: 10
+ *   },
+ *   countText: {
+ *     color: '#FF00FF'
+ *   }
+ * })
+ *
+ * AppRegistry.registerComponent('App', () => App)
+ * ```
+ * 
  */
 
 var TouchableHighlight = createReactClass({

Libraries/Components/Touchable/TouchableOpacity.js

@@ -64,21 +64,21 @@ var PRESS_RETENTION_OFFSET = {top: 20, left: 20, right: 20, bottom: 30};
  * } from 'react-native'
  *
  * class App extends Component {
- * constructor(props) {
+ *   constructor(props) {
- *  super(props)
+ *     super(props)
- *  this.state = { count: 0 }
+ *     this.state = { count: 0 }
- * }
+ *   }
  *
- * onPress = () => {
+ *   onPress = () => {
- *   this.setState({
+ *     this.setState({
- *     count: this.state.count+1
+ *       count: this.state.count+1
- *   })
+ *     })
- * }
+ *   }
  *
  *  render() {
- *     return (
+ *    return (
- *       <View style={styles.container}>
+ *      <View style={styles.container}>
- *         <TouchableOpacity
+ *        <TouchableOpacity
  *          style={styles.button}
  *          onPress={this.onPress}
  *        >