chore(vue): Update README for Vue 3 (#3832)

Author: AbhiPrasad

packages/vue/README.md

@@ -17,9 +17,22 @@
 This package is a wrapper around `@sentry/browser`, with added functionality related to Vue.js. All methods available in
 `@sentry/browser` can be imported from `@sentry/vue`.
 
-It targets Vue version `2.x`. Support for `3.x` is tracked by [GitHub issue #2925](https://github.com/getsentry/sentry-javascript/issues/2925).
+To use this SDK, call `Sentry.init(options)` as early in your application as possible.
 
-To use this SDK, call `Sentry.init(options)` before you create a new Vue instance.
+### Vue 3
+
+```javascript
+const app = createApp({
+  // ...
+});
+
+Sentry.init({
+  app,
+  dsn: '__PUBLIC_DSN__',
+});
+```
+
+### Vue 2
 
 ```javascript
 import Vue from 'vue'