[VarDumper] Doc for the Data::seek() method

Author: nicolas-grekas

components/var_dumper/advanced.rst

@@ -74,6 +74,9 @@ Before dumping it, you can further limit the resulting
 :method:`Symfony\\Component\\VarDumper\\Cloner\\Data::withRefHandles`
     Allows removing internal objects' handles for sparser output (useful for tests).
 
+:method:`Symfony\\Component\\VarDumper\\Cloner\\Data::seek`
+    Allows dumping only subparts of already cloned arrays, objects or resources.
+
 Unlike the previous limits on cloners that remove data on purpose, these can
 be changed back and forth before dumping since they do not affect the
 intermediate representation internally.
@@ -82,7 +85,11 @@ intermediate representation internally.
 
     When no limit is applied, a :class:`Symfony\\Component\\VarDumper\\Cloner\\Data`
     object is as accurate as the native :phpfunction:`serialize` function,
-    and thus could be for purposes beyond dumping for debugging.
+    and thus could be used for purposes beyond debugging.
+
+.. versionadded:: 3.2
+    The :method:`Symfony\\Component\\VarDumper\\Cloner\\Data::seek` method has been
+    added in Symfony 3.2
 
 Dumpers
 -------