test(local-storage): add unit tests

tests/LocalStorage/LocalStorage.test.svelte

@@ -0,0 +1,19 @@
+<svelte:options accessors />
+
+<script lang="ts">
+  import { LocalStorage } from "carbon-components-svelte";
+
+  // Example values for testing
+  const primitiveValue = "test-value";
+  const objectValue = { theme: "dark", fontSize: 16 };
+</script>
+
+<!-- Default local storage -->
+<div data-testid="default-storage">
+  <LocalStorage value={primitiveValue} />
+</div>
+
+<!-- Local storage with object value -->
+<div data-testid="storage-object">
+  <LocalStorage key="theme-settings" value={objectValue} />
+</div>