Clarify that rules.pl goes in refs/meta/config

Bug: Issue 9691
Change-Id: I9e80b7d3d441fbd1a6fd3cade8d9803643ddd89e
diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index fa046cc..5974482 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md
@@ -8,7 +8,9 @@
 predicates for Gerrit projects.
 
 If a Gerrit project wants to enforce this *owner-approval* policy,
-it can add a `submit_rule` to its `rules.pl` file like this:
+it can add a `submit_rule` to the [`rules.pl`
+file](https://gerrit-review.googlesource.com/Documentation/config-project-config.html#file-rules_pl)
+in `refs/meta/config` like this:
 
 ```prolog
 submit_rule(S) :- find_owners:submit_rule(S).