Describe slot attribute (#1402)

* Describe slto attribute

Editorial / linking.
Fix #1256
Depends on #1403

* fix links

need to refer by version specifically

sections/dom.include

@@ -2484,7 +2484,7 @@ console.assert(image.height === 200);
   attribute's value must be a [=set of space-separated tokens=]
   representing the various classes that the element belongs to.
 
-  The DOM specification defines additional user agent requirements for this attribute. [[DOM41]]
+  The DOM specification defines additional user agent requirements for this attribute. [[DOM]]
 
   <div class="note">
     Assigning classes to an element affects class matching in selectors in CSS, the
@@ -2499,7 +2499,7 @@ console.assert(image.height === 200);
   attribute value must be unique amongst all the [=IDs=] in the element's [=tree=]
   and must contain at least one character. The value must not contain any [=space characters=].
 
-  The DOM specification defines additional user agent requirements for this  attribute. [[DOM41]]
+  The DOM specification defines additional user agent requirements for this attribute. [[DOM]]
 
   <div class="note">
     The <{global/id}> attribute specifies its element's [=id|unique identifier (ID)=].
@@ -2524,7 +2524,11 @@ console.assert(image.height === 200);
 
   There are no conformance requirements for the <dfn element-attr for="global"><code>slot</code></dfn>
   attribute specific to [=HTML elements=]. The DOM specification defines requirements for this
-  attribute. [[DOM41]]
+  attribute. [[DOM]]
+
+  <p class="note">The <{global/slot}> attribute is used for elements in <a>shadow trees</a>,
+  to <a>assign a slot</a> for the element. The slot will be assigned to the <{slot}>
+  element whose <{slot/name}> attribute matches the value of the <{global/slot}> attribute.</p>
 
   <hr />
 

single-page.bs

@@ -445,7 +445,7 @@ urlPrefix: https://drafts.csswg.org/cssom/#; type: dfn; spec: CSSOM;
 
 # ************************************ DOM **************************************************
 
-urlPrefix: https://www.w3.org/TR/dom/#; spec: DOM
+urlPrefix: https://www.w3.org/TR/dom41/#; spec: DOM
     type:interface; url: document
         text:Document
     urlPrefix: concept-; type: dfn
@@ -493,6 +493,7 @@ urlPrefix: https://www.w3.org/TR/dom/#; spec: DOM
         text: shadow including tree order
     urlPrefix: interface-; type: interface
         text: Element
+    text: assign a slot; type: dfn
     text: represented by the collection; type: dfn
     text: ShadowRoot; type: interface
     url: node-remove; type: dfn