[TASK] Show information that VH allows arbitrary arguments (#658)

Resolves #657

Author: linawolf

packages/typo3-docs-theme/resources/template/body/directive/viewhelper.html.twig

@@ -27,8 +27,16 @@
     {% include "body/directive/viewhelper/viewhelper-source.html.twig" %}
 {% endif %}
 
-{% if node.arguments %}
+{% if node.arguments or node.allowsArbitraryArguments %}
     <h2>Arguments</h2>
+
+    {% if node.allowsArbitraryArguments %}
+        <div class="admonition info" role="alert">
+            <p class="admonition-title">Allows arbitrary arguments</p>
+            <p>This ViewHelper allows you to pass arbitrary arguments not defined below directly
+                to the HTML tag created. This includes custom `data-` arguments.</p>
+        </div>
+    {% endif %}
     <p>The following arguments are available for the {{ node.tagName }} ViewHelper: </p>
     {% for argument in node.arguments  %}
         {% include "body/directive/viewhelper/viewhelper-argument.html.twig" %}

tests/Integration/tests/viewhelper/expected/index.html

@@ -95,7 +95,8 @@ <h2>Source code</h2>
 </p>
 
     <h2>Arguments</h2>
-    <p>The following arguments are available for the split ViewHelper: </p>
+
+        <p>The following arguments are available for the split ViewHelper: </p>
             <dl class="confval">
     <dt id="viewhelper-argument-typo3fluid-fluid-viewhelpers-splitviewhelper-value" class="d-flex justify-content-between">
         <div class="confval-header">
@@ -233,7 +234,13 @@ <h2>Source code</h2>
 </p>
 
     <h2>Arguments</h2>
-    <p>The following arguments are available for the link.external ViewHelper: </p>
+
+            <div class="admonition info" role="alert">
+            <p class="admonition-title">Allows arbitrary arguments</p>
+            <p>This ViewHelper allows you to pass arbitrary arguments not defined below directly
+                to the HTML tag created. This includes custom `data-` arguments.</p>
+        </div>
+        <p>The following arguments are available for the link.external ViewHelper: </p>
             <dl class="confval">
     <dt id="viewhelper-argument-typo3-cms-fluid-viewhelpers-link-externalviewhelper-uri" class="d-flex justify-content-between">
         <div class="confval-header">