Add the usage of --setup-show in conjunction with --querycount to the docs

Author: renanivo

docs/usage.rst

@@ -35,6 +35,10 @@ Fail tests that render templates which make use of invalid template variables.
 Show a list of top N tests which executed most queries. Use `--querycount=0`
 to display a list of all tests ordered by the number of queries executed.
 
+Using it in conjunction with `--setup-show` will display the number of
+queries executed by each fixture (when the number of queries executed by the
+fixture is greater than zero).
+
 Running tests in parallel with pytest-xdist
 -------------------------------------------
 pytest-django supports running tests on multiple processes to speed up test