docs for cache_dir ini option

Author: RockBomber

doc/en/cache.rst

@@ -1,3 +1,5 @@
+.. _`cache_provider`:
+
 Cache: working with cross-testrun state
 =======================================
 

doc/en/customize.rst

@@ -243,7 +243,6 @@ Builtin configuration file options
    from ``pytest.ini``/``tox.ini``/``setup.cfg`` of the project if any,
    or up to the file-system root.
 
-
 .. confval:: filterwarnings
 
    .. versionadded:: 3.1
@@ -262,3 +261,13 @@ Builtin configuration file options
 
    This tells pytest to ignore deprecation warnings and turn all other warnings
    into errors. For more information please refer to :ref:`warnings`.
+
+.. confval:: cache_dir
+
+   .. versionadded:: 3.2
+
+   Sets a directory where stores content of cache plugin. Default directory is
+   ``.cache`` which is created in :ref:`rootdir <rootdir>`. Directory may be
+   relative or absolute path. If setting relative path, then directory is created
+   relative to :ref:`rootdir <rootdir>`. For more information about cache plugin
+   please refer to :ref:`cache_provider`.