feat(docs): update docs on Guess.js

docs/docs/optimizing-plugins-with-guessjs.md

@@ -0,0 +1,23 @@
+---
+title: Optimizing plugins with Guess.js
+---
+
+Pre-loading resources is a great way to improve application performance. However, pre-loading everything on a page can waste bandwidth. This is especially true for mobile phone users who may have limited data and bandwidth. So how do you know which resources to pre-load? Is it just a guessing game? Not anymore.
+
+## Introducing Guess.js
+
+By leveraging Google Analytics data and machine learning, [Guess.js](https://github.com/guess-js/guess) is able determine which pages a user is most likely to navigate to from the current page and only pre-load those resources. Thus, there are fewer network requests which improves performance on slower networks.
+
+## How does it work?
+
+Guess.js will download a file from Google Analytics during the production build. This file is then used to construct the model for predictive analytics.
+
+## Guess.js and Gatsby
+
+See the [Gatsby Guess.js Plugin](https://www.gatsbyjs.org/packages/gatsby-plugin-guess-js) for more information on integrating Guess.js with Gatsby.
+
+### References:
+
+- [Introducing Guess.js](https://blog.mgechev.com/2018/05/09/introducing-guess-js-data-driven-user-experiences-web/)
+- [Gatsby Plugin Guess.js](https://github.com/gatsbyjs/gatsby/tree/master/packages/gatsby-plugin-guess-js)
+- [Cutting Edge Static Sites](https://www.contentful.com/blog/2018/06/13/journey-cutting-edge-static-sites-gatsbyjs-v2/)

www/src/data/sidebars/doc-links.yaml

@@ -243,6 +243,8 @@
           link: /docs/seo/
         - title: Optimize Prefetching with Guess.js*
           link: /docs/optimize-prefetching-with-guessjs/
+        - title: Optimizing Plugins with Guess.js*
+          link: /docs/optimizing-plugins-with-guessjs/
 - title: Ecosystem
   link: /ecosystem/
   items: