docs: add vercel analytics

docs/package.json

@@ -15,6 +15,7 @@
     "@animxyz/core": "^0.6.6",
     "@animxyz/vue3": "^0.6.7",
     "@stackblitz/sdk": "^1.8.0",
+    "@vercel/analytics": "^0.1.5",
     "@vue-flow/additional-components": "workspace:*",
     "@vue-flow/core": "workspace:*",
     "@vue/repl": "1.1.2",

docs/src/.vitepress/theme/index.ts

@@ -1,6 +1,7 @@
 import type { Theme } from 'vitepress'
 import VueAnimXyz from '@animxyz/vue3'
 import DefaultTheme from 'vitepress/theme'
+import { inject } from '@vercel/analytics'
 import Layout from './layouts/default.vue'
 import 'virtual:windi.css'
 import '@animxyz/core'
@@ -13,6 +14,7 @@ const CustomTheme = {
   Layout,
   enhanceApp: ({ app }) => {
     app.use(VueAnimXyz)
+    inject()
   },
 } as Theme