docs: change parameter descriptions to numbered list

Author: kenjis

user_guide_src/source/libraries/validation.rst

@@ -690,8 +690,13 @@ Your new custom rule could now be used just like any other rule:
 Allowing Parameters
 -------------------
 
-If your method needs to work with parameters, the function will need a minimum of three parameters: the value to validate,
-the parameter string, and an array with all of the data that was submitted the form. The ``$data`` array is especially handy
+If your method needs to work with parameters, the function will need a minimum of three parameters:
+
+1. the value to validate (``$value``)
+2. the parameter string (``$params``)
+3. an array with all of the data that was submitted the form (``$data``)
+
+The ``$data`` array is especially handy
 for rules like ``required_with`` that needs to check the value of another submitted field to base its result on:
 
 .. literalinclude:: validation/037.php