[DOCS] Link custom rule pages

Author: lcawl

docs/en/stack/ml/rules.asciidoc

@@ -36,4 +36,4 @@ Alternatively, you can make it trigger only when the field value does not match
 one of the filter values. You therefore have much greater control over which 
 anomalous events affect the {ml} model and appear in the {ml} results. 
 
-//TO-DO: Add link to more information about defining rules.
+For more information, see <<ml-configuring-detector-custom-rules>>.