Update README.md (#4764)

* Update README.md

* Update README.md

Author: calcsam

packages/gatsby-plugin-react-helmet/README.md

@@ -7,7 +7,9 @@ React Helmet is a component which lets you control your document head using
 their React component.
 
 With this plugin, attributes you add in their component, e.g. title, meta
-attributes, etc. will get added to the static HTML pages Gatsby builds.
+attributes, etc. will get added to the static HTML pages Gatsby builds. 
+
+This is important not just for site viewers, but also for SEO -- title and description metadata stored in the document head is a key component used by Google in determining placement in search results.
 
 ## Install
 
@@ -20,3 +22,8 @@ Just add the plugin to the plugins array in your `gatsby-config.js`
 ```javascript
 plugins: [`gatsby-plugin-react-helmet`];
 ```
+
+## Examples
+
+[GatsbyJS.org](https://github.com/gatsbyjs/gatsby/blob/master/www/src/layouts/index.js)
+[Jason Lengstorf personal website](https://github.com/jlengstorf/lengstorf.com/blob/master/src/components/SEO.js)