Actually enable Google Analytics for Corso docs (#1409)

## Description

We were missing the actual plugin and did not have configuration for the right
plugin type.

## Type of change

- [x] 🐛 Bugfix
- [x] 🗺️ Documentation

docs/docusaurus.config.js

@@ -50,7 +50,7 @@ const config = {
             'https://github.com/alcionai/corso/tree/main/docs',
         },
         blog: false,
-        googleAnalytics: {
+        gtag: {
           trackingID: 'G-4EXT1PY6KC',
         },
         theme: {

docs/package-lock.json

@@ -9,6 +9,7 @@
       "version": "0.1.0",
       "dependencies": {
         "@docusaurus/core": "2.2.0",
+        "@docusaurus/plugin-google-gtag": "^2.2.0",
         "@docusaurus/preset-classic": "2.2.0",
         "@mdx-js/react": "^2.1.5",
         "clsx": "^1.2.1",

docs/package.json

@@ -15,6 +15,7 @@
   },
   "dependencies": {
     "@docusaurus/core": "2.2.0",
+    "@docusaurus/plugin-google-gtag": "^2.2.0",
     "@docusaurus/preset-classic": "2.2.0",
     "@mdx-js/react": "^2.1.5",
     "clsx": "^1.2.1",