inject css in head to prevent content shift when using SSR, fixes inertiajs#1760

Author: buhrmi

playgrounds/svelte5/vite.config.js

@@ -9,6 +9,10 @@ export default defineConfig({
       ssr: 'resources/js/ssr.js',
       refresh: true,
     }),
-    svelte(),
+    svelte({
+      compilerOptions: {
+        css: 'injected'
+      }
+    }),
   ],
 })