fix: replace Form N headings with function signatures matching jQuery API style

Replace unclear "Form 1", "Form 2", "Form 3" headings with descriptive
function signatures (e.g., `required()`, `required( dependency-expression )`)
styled with gray background headers and light body blocks to match the
original jQuery API documentation layout.

Files changed:
- _layouts/default.html: add .signature and .signature-body CSS classes
- _entries/required-method.md: 3 signature forms
- _entries/rules.md: 3 signature forms
- _entries/jQuery.validator.addClassRules.md: 2 signature forms

Author: Copilot

_entries/jQuery.validator.addClassRules.md

@@ -13,7 +13,10 @@ Add a compound class method - useful to refactor common combinations of rules in
 
 ## Usage
 
-### Form 1
+### `jQuery.validator.addClassRules( name, rules )`
+{:.signature}
+
+<div class="signature-body" markdown="1">
 
 **name** *(String)*
 
@@ -23,12 +26,19 @@ The name of the class rule to add
 
 The compound rules (see example)
 
-### Form 2
+</div>
+
+### `jQuery.validator.addClassRules( rules )`
+{:.signature}
+
+<div class="signature-body" markdown="1">
 
 **rules** *(Object)*
 
 A map of className-rules pairs (see example).
 
+</div>
+
 ## Examples
 
 ### Example 1

_entries/required-method.md

@@ -17,26 +17,37 @@ Return false, if the element is empty (text input) or unchecked (radio/checkbox)
 
 ## Usage
 
-### Form 1
+### `required()`
+{:.signature}
 
-The element is always required.
+<div class="signature-body" markdown="1">
 
-### Form 2
+This signature does not accept any arguments.
 
-Makes the element required, depending on the result of the given expression.
+</div>
+
+### `required( dependency-expression )`
+{:.signature}
+
+<div class="signature-body" markdown="1">
 
 **dependency-expression** *(String)*
 
 An expression (String) that is evaluated in the context of the element's form, making the field required only if the expression returns more than one element. Very often your expression will use selector filters such as `#foo:checked`, `#foo:filled`, `#foo:visible`. This plugin provides [custom selectors for that purpose](/documentation#custom-selectors).
 
-### Form 3
+</div>
 
-Makes the element required, depending on the result of the given callback.
+### `required( dependency-callback )`
+{:.signature}
+
+<div class="signature-body" markdown="1">
 
 **dependency-callback** *(Function)*
 
 The function is executed with the element as it's only argument: If it returns true, the element is required.
 
+</div>
+
 ## Examples
 
 ### Example 1

_entries/rules.md

@@ -17,30 +17,41 @@ Returns the validations rules for the first selected element or Adds the specifi
 
 ## Usage
 
-### Form 1
+### `.rules()`
+{:.signature}
 
-Read rules for the first element
+<div class="signature-body" markdown="1">
 
-### Form 2
+Returns the validation rules for the first selected element.
 
-Add rules
+</div>
+
+### `.rules( "add", rules )`
+{:.signature}
+
+<div class="signature-body" markdown="1">
 
 **"add"** *(String)*
 
 **rules** *(Object)*
 
 The rules to add. Accepts the same format as the rules-option of the validate-method.
 
-### Form 3
+</div>
 
-Remove rules
+### `.rules( "remove", rules )`
+{:.signature}
+
+<div class="signature-body" markdown="1">
 
 **"remove"** *(String)*
 
 **rules** *(Object)*
 
 The space-seperated names of rules to remove and return. If left unspecified, removes and returns all rules. Manipulates only rules specified via rules-option or via rules("add").
 
+</div>
+
 ## Examples
 
 ### Example 1

_layouts/default.html

@@ -134,6 +134,29 @@
         iframe {
             max-width: 100%;
         }
+        /* Function signature headers – styled to match the original jQuery API docs */
+        .signature {
+            background-color: #808080;
+            color: #fff;
+            padding: 8px 12px;
+            font-size: 1em;
+            font-weight: bold;
+            border-radius: 3px;
+            margin-top: 1.5em;
+        }
+        .signature code {
+            background-color: transparent;
+            color: #fff;
+            font-size: 1em;
+            padding: 0;
+        }
+        /* Content block beneath a signature header */
+        .signature-body {
+            background-color: #f0f0f0;
+            border-left: 4px solid #808080;
+            padding: 12px 16px;
+            margin-bottom: 1.5em;
+        }
     </style>
 </head>
 <body>