Document deprecation of tempstorage.

CHANGES.rst

@@ -4,7 +4,12 @@ Changelog
 5.1 (unreleased)
 ----------------
 
-- Nothing changed yet.
+- Package is now officially deprecated as it was broken for many years. This 
+  was/ is common knowledge in the zope community, but was not documented 
+  anywhere and thus this package was still used by many community members 
+  without knowing this. See
+  (`#8 <https://github.com/zopefoundation/tempstorage/issues/8>`_)
+  (`#12 <https://github.com/zopefoundation/tempstorage/issues/12>`_)
 
 
 5.0 (2019-05-10)