Enable using Prism for syntax highlighting (#735)

* Enable user to use prism.js as syntax highlighter

* add package-lock

* if 'usePrism' is true, use prismjs on all languages

* don't get lang by hljs if use prism

* Update api-site-config.md

* Update api-doc-markdown.md

* only load prism css when usePrism is true

docs/api-doc-markdown.md

@@ -180,3 +180,31 @@ While Highlight.js provides support for [many popular languages out of the box](
   }
 }
 ```
+
+### Using Prism as additional syntax highlighter
+
+While highlight.js supports a lot of languages, you can opt to use Prism to syntax highlight certain languages available in the list [here](https://github.com/PrismJS/prism/tree/master/components). Include those languages in `usePrism` field in your [siteConfig.js](api-site-config.md)
+
+Example:
+```
+// siteConfig.js
+usePrism: ['jsx']
+```
+
+Notice that the code block below uses JSX syntax highlighting from Prism.
+
+```jsx
+class Example extends React.Component {
+  render() {
+    return (
+      <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
+        <Text>Docusaurus</Text>
+        <Button
+          title="Click me"
+          onPress={() => this.props.navigation.push('Docusaurus')}
+        />
+      </View>
+    );
+  }
+}
+```