Add missing property for Google Analytics in documentation

Author: Julien Neuhart

docs/docusaurus.config.js

@@ -7,6 +7,7 @@ module.exports = {
   favicon: 'img/favicon.ico',
   organizationName: 'thecodingmachine', // Usually your GitHub org/user name.
   projectName: 'symfony-boilerplate', // Usually your repo name.
+  plugins: ['@docusaurus/plugin-google-analytics'],
   themeConfig: {
     googleAnalytics: {
       trackingID: 'G-ZGCNWVF92C',