Add Inertia version to upgrade guide

Author: timacdonald

UPGRADE.md

@@ -99,7 +99,13 @@ Vite only supports ES modules, so if you are upgrading an existing application y
 
 #### Inertia
 
-Inertia makes use of a `require()` call that is more complex to replicate with Vite.
+Ensure you have updated to at least version `0.6.3` of the `inertia-laravel` package:
+
+```sh
+composer require inertiajs/inertia-laravel:^0.6.3
+```
+
+Additionally, Inertia makes use of a `require()` call that is more complex to replicate with Vite.
 
 The following function can be used instead: