Add example on Components

Summary:
<!--
Thank you for sending the PR! We appreciate you spending the time to work on these changes.

Help us understand your motivation by explaining why you decided to make this change.

You can learn more about contributing to React Native here: http://facebook.github.io/react-native/docs/contributing.html

Happy contributing!

-->

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 facebook#15950

Differential Revision: D5881366

Pulled By: hramos

fbshipit-source-id: 2926071723defedf9ed5cb1b1128204256c71dd9

Author: lwinkyawmyat

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) {
- *  super(props)
- *  this.state = { count: 0 }
- * }
+ *   constructor(props) {
+ *     super(props)
+ *     this.state = { count: 0 }
+ *   }
  *
- * onPress = () => {
- *   this.setState({
- *     count: this.state.count+1
- *   })
- * }
+ *   onPress = () => {
+ *     this.setState({
+ *       count: this.state.count+1
+ *     })
+ *   }
  *
  *  render() {
- *     return (
- *       <View style={styles.container}>
- *         <TouchableOpacity
+ *    return (
+ *      <View style={styles.container}>
+ *        <TouchableOpacity
  *          style={styles.button}
  *          onPress={this.onPress}
  *        >