feat: Define the relation between a document’s type and prototype

Author: ExE-Boss

source

@@ -9313,6 +9313,12 @@ o.myself = o;</code></pre>
   that can be set when the <code>Document</code> is created. If it is not explicitly set, then its
   value is the empty string.</p>
 
+  <p>A <code>Document</code> instance with its <span data-x="concept-document-type">type</span>
+  set to "<code>html</code>" inherits from <code>HTMLDocument</code>.</p>
+
+  <p>A <code>Document</code> instance with its <span data-x="concept-document-type">type</span>
+  set to "<code data-x="">xml</code>" inherits from <dfn data-x-href="https://dom.spec.whatwg.org/#xmldocument">
+  <code>XMLDocument</code></dfn>.</p>
 
   <h4>The <code>Document</code> object</h4>