minor #18571 add OptionsResolverIntrospectorusage doc (PululuK)

This PR was submitted for the 6.4 branch but it was squashed and merged into the 5.4 branch instead.

Discussion
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add `OptionsResolverIntrospector`usage doc

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Original commit : symfony/symfony@d6d187d
Orignal PR : symfony/symfony#24208

Commits
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887f6f5 add `OptionsResolverIntrospector`usage doc

Author: javiereguiluz

components/options_resolver.rst

@@ -944,3 +944,24 @@ method ``clearOptionsConfig()`` and call it periodically::
 
 That's it! You now have all the tools and knowledge needed to process
 options in your code.
+
+Get More Insights
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The `OptionsResolverIntrospector` inspect options definitions inside an `OptionsResolver` instance.
+
+method::
+
+   use Symfony\Component\OptionsResolver\Debug\OptionsResolverIntrospector;
+   use Symfony\Component\OptionsResolver\OptionsResolver;
+
+    $resolver = new OptionsResolver();
+    $resolver->setDefaults([
+        'host' => 'smtp.example.org',
+        'port' => 25,
+    ]);
+
+    $introspector = new OptionsResolverIntrospector($resolver);
+    $introspector->getDefault('host'); // Retrieves "smtp.example.org"
+
+