fix: add nikic/php-parser requirement for translation:extract in translation.rst

Author: bsramin

translation.rst

@@ -457,6 +457,16 @@ The ``translation:extract`` command looks for missing translations in:
 * Any PHP file/class stored in the ``src/`` directory that uses
   :ref:`Constraints Attributes <validation-constraints>`  with ``*message`` named argument(s).
 
+To read PHP files, is used the new ``PhpAstExtractor`` service supports all kinds of trans() function calls, usages of TranslatableMessage class, messages defined in validation constraints, etc...
+
+To use the new translation extractor, install the ``nikic/php-parser`` package using Composer, before using `translation:extract`.
+
+
+.. code-block:: terminal
+
+    $ composer require nikic/php-parser
+
+
 .. _translation-resource-locations:
 
 Translation Resource/File Names and Locations