minor #371 Add LiveProp because I got an error otherwise (michaelKaefer, kbond)

This PR was merged into the 2.x branch.

Discussion
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Add LiveProp because I got an error otherwise

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| Tickets       | -
| License       | MIT

Commits
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1a39b51 Update src/LiveComponent/src/Resources/doc/index.rst
ddd1f0f Add LiveProp because I got an error otherwise

Author: kbond

src/LiveComponent/src/Resources/doc/index.rst

@@ -16,12 +16,14 @@ A real-time product search component might look like this::
 
     use Symfony\UX\LiveComponent\Attribute\AsLiveComponent;
     use Symfony\UX\LiveComponent\DefaultActionTrait;
+    use Symfony\UX\LiveComponent\Attribute\LiveProp;
 
     #[AsLiveComponent('product_search')]
     class ProductSearchComponent
     {
         use DefaultActionTrait;
 
+        #[LiveProp(writable: true)]
         public string $query = '';
 
         private ProductRepository $productRepository;