Update docs

docs/20_Checks/_index.md

@@ -32,6 +32,7 @@ There is one include script used by all checks:
 * check_proc_mem
 * check_proc_ressources
 * check_proc_zombie
+* [check_psqlserver](check_psqlserver.md)
 * [check_reboot_required](check_reboot_required.md)
 * check_sensuplugins
 * check_smartstatus