move config into svelte.config.js (#16265)

playgrounds/sandbox/svelte.config.js

@@ -0,0 +1,5 @@
+export default {
+	compilerOptions: {
+		hmr: true
+	}
+};

playgrounds/sandbox/vite.config.js

@@ -7,14 +7,7 @@ export default defineConfig({
 		minify: false
 	},
 
-	plugins: [
-		inspect(),
-		svelte({
-			compilerOptions: {
-				hmr: true
-			}
-		})
-	],
+	plugins: [inspect(), svelte()],
 
 	optimizeDeps: {
 		// svelte is a local workspace package, optimizing it would require dev server restarts with --force for every change