docs: add Google Analaytics

docs/.vuepress/config.js

@@ -1,4 +1,5 @@
-const { description } = require('../../package')
+const { description } = require('../../package');
+const GTM_TAG = 'GTM-WMDC3CP';
 
 module.exports = {
   title: 'Vue Storefront 2 for Odoo',
@@ -8,7 +9,16 @@ module.exports = {
     ['link', { rel: 'icon', href: '/favicon.png' }],
     ['meta', { name: 'theme-color', content: '#3eaf7c' }],
     ['meta', { name: 'apple-mobile-web-app-capable', content: 'yes' }],
-    ['meta', { name: 'apple-mobile-web-app-status-bar-style', content: 'black' }]
+    ['meta', { name: 'apple-mobile-web-app-status-bar-style', content: 'black' }],
+
+    // Google Tag Manager
+    ['script', {}, [`
+      (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
+      new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
+      j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
+      'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
+      })(window,document,'script','dataLayer','${GTM_TAG}');
+    `]],
   ],
   configureWebpack: (config) => {
     config.module.rules = config.module.rules.map(rule => ({
@@ -38,6 +48,7 @@ module.exports = {
     '@vuepress/search'
   ],
   themeConfig: {
+    GTM_TAG,
     repo: 'https://github.com/vuestorefront-community/odoo/',
     editLinks: true,
     docsDir: 'docs',