Base URL in Vite Example should be 'absolute'

If you don't add a slash in front, it will attempt to import the assets relative to the current URL pathname.

https://github.com/CesiumGS/cesium-vite-example/blob/main/vite.config.js#L7

The example should add the slash in front, and/or explain this limitation.

Open vite.config.js at line 7 and inspect how the example sets its base URL for asset imports. Confirm the behavior when the URL lacks a leading slash, then update the example and/or its explanation so the intended absolute-base behavior is clear.

Written by the indexing model from the issue text.