docs: add empty line

Author: kenjis

user_guide_src/source/libraries/caching.rst

@@ -52,6 +52,7 @@ $ttl
 ----
 
 The default number of seconds to save items when none is specified.
+
 WARNING: This is not used by framework handlers where 60 seconds is hard-coded, but may be useful
 to projects and modules. This will replace the hard-coded value in a future release.