Merge branch '5.4' into 6.2

* 5.4:
  [Standards] Add `Attribute` format and formats for Code Examples

Author: javiereguiluz

contributing/documentation/standards.rst

@@ -92,6 +92,7 @@ Configuration examples should show all supported formats using
 * **Validation**: Attributes, YAML, XML, PHP
 * **Doctrine Mapping**: Attributes, YAML, XML, PHP
 * **Translation**: XML, YAML, PHP
+* **Code Examples** (if applicable): PHP Symfony, PHP Standalone
 
 Example
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