Add gatsby-plugin-feed

gatsby-config.js

@@ -2,6 +2,8 @@ module.exports = {
   siteMetadata: {
     title: "Gatsby Starter Blog",
     author: "Kyle Mathews",
+    description: "A starter blog demonstrating what Gatsby can do.",
+    siteUrl: "https://gatsbyjs.github.io/gatsby-starter-blog/",
   },
   plugins: [
     {
@@ -41,6 +43,7 @@ module.exports = {
         //trackingId: `ADD YOUR TRACKING ID HERE`,
       },
     },
+    `gatsby-plugin-feed`,
     `gatsby-plugin-offline`,
     `gatsby-plugin-react-helmet`,
     {