Add prettier and re-configure lint according to current best practises

tests-e2e/cypress/plugins/index.js

@@ -1,3 +1,4 @@
+/* eslint-env node */
 // ***********************************************************
 // This example plugins/index.js can be used to load plugins
 //
@@ -11,7 +12,8 @@
 // This function is called when a project is opened or re-opened (e.g. due to
 // the project's config changing)
 
+// eslint-disable-next-line no-unused-vars
 module.exports = (on, config) => {
   // `on` is used to hook into various events Cypress emits
   // `config` is the resolved Cypress config
-}
+};