minor #861 [LiveComponent] Added type mixed to $value property and added string $className to mach HydrationExtensionInterface (mwansinck)

This PR was merged into the 2.x branch.

Discussion
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[LiveComponent] Added type mixed to $value property and added string $className to mach HydrationExtensionInterface

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

Documentation example for writing the hydrate method was not compatible with the HydrationExtensionInterface.
Corrected the example so the code can be copy-pasted without errors.

Commits
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4b29a1f Added type mixed to $value property and added string $className to match HydrationExtensionInterface

Author: weaverryan

src/LiveComponent/doc/index.rst

@@ -700,7 +700,7 @@ a custom ``Food`` object, a hydration extension might look like this::
             return is_subclass_of($className, Food::class);
         }
 
-        public function hydrate($value)
+        public function hydrate(mixed $value, string $className): ?object
         {
             return new Food($value['name'], $value['isCooked']);
         }