Update README.md (#234)

Author: gregfenton

README.md

@@ -21,6 +21,9 @@ Register tasks in your `cypress/plugins/index.js` file
 ```js
 module.exports = (on, config) => {
   require('@cypress/code-coverage/task')(on, config)
+  
+  // add other tasks to be registered here
+  
   // IMPORTANT to return the config object
   // with the any changed environment variables
   return config