feat: Add Stack Pack for Next.js

This commit adds a Lighthouse Stack Pack for Next.js based on
documentation and recommendations on Next.js website.

CONTRIBUTING.md

@@ -23,7 +23,7 @@ Want to submit a brand new stack pack? Awesome! In order for a stack pack to be
 - A significant number of websites (~ in the 10's of thousands) should be using the stack. Consider using [HTTP Archive](https://discuss.httparchive.org/t/javascript-library-detection/955/2) to detect the number sites used by the particular tool.
 - There must be a minimum of two maintainers for each stack from the community who can help review and provide suggestions. We (Google) should not be the ones to decide what the audit recommendations should be.
 
-If all of these are met, submit a PR for review! Copy the `general.json` file into the `packs/` directory and change each audit string to a specific recommendation regarding your stack. If you can't provide a recommendation for a particular audit, change it to an empty string. However, you will need to provide at least 6 audit strings as mentioned earlier.
+If all of these are met, submit a PR for review! Copy the `general.js` file into the `packs/` directory and change each audit string to a specific recommendation regarding your stack. If you can't provide a recommendation for a particular audit, change it to an empty string. However, you will need to provide at least 6 audit strings as mentioned earlier.
 
 ## Submitting changes to audit strings
 

README.md

@@ -18,6 +18,7 @@ Many developers today use different technologies (backend/CMS/JavaScript framewo
 * Angular
 * AMP
 * Magento
+* Next.js
 
 ## Contributing
 

index.js

@@ -1,12 +1,13 @@
 const stackPacks = [
-  require('./packs/wordpress.js'),
-  require('./packs/drupal.js'),
-  require('./packs/react.js'),
-  require('./packs/angular.js'),
   require('./packs/amp.js'),
-  require('./packs/magento.js'),
+  require('./packs/angular.js'),
+  require('./packs/drupal.js'),
   require('./packs/joomla.js'),
+  require('./packs/magento.js'),
+  require('./packs/next.js'),
   require('./packs/octobercms.js'),
+  require('./packs/react.js'),
+  require('./packs/wordpress.js'),
 ];
 
 module.exports = stackPacks;