Meta: make it easier to reference participate in a tree

PR: #216

dom.bs

@@ -234,7 +234,7 @@ A <dfn export id=concept-tree>tree</dfn> is a finite hierarchical tree structure
 traversal of a <a>tree</a>.
 <!-- https://en.wikipedia.org/wiki/Depth-first_search -->
 
-An object that <dfn export for=tree id=concept-tree-participate lt="participate">participates</dfn> in
+An object that <dfn export for=tree id=concept-tree-participate lt="participate|participate in a tree|participates in a tree">participates</dfn> in
 a <a>tree</a> has a
 <dfn export for=tree id=concept-tree-parent>parent</dfn>, which is either another object
 or null, and an ordered list of zero or more
@@ -9671,6 +9671,7 @@ Jake Verbaten,
 James Graham,
 James Greene,
 James Robinson,
+Jeffrey Yasskin,
 Jens Lindström,
 Jesse McCarthy,
 João Eiras,

dom.html

@@ -292,7 +292,7 @@ <h2 class="heading settled" data-level="2" id="terminology"><span class="secno">
    <h3 class="heading settled" data-level="2.1" id="trees"><span class="secno">2.1. </span><span class="content">Trees</span><a class="self-link" href="#trees"></a></h3>
    <p>A <dfn data-dfn-type="dfn" data-export="" id="concept-tree">tree<a class="self-link" href="#concept-tree"></a></dfn> is a finite hierarchical tree structure. In <dfn data-dfn-type="dfn" data-export="" id="concept-tree-order">tree order<a class="self-link" href="#concept-tree-order"></a></dfn> is preorder, depth-first
 traversal of a <a data-link-type="dfn" href="#concept-tree">tree</a>.</p>
-   <p>An object that <dfn data-dfn-for="tree" data-dfn-type="dfn" data-export="" data-lt="participate" id="concept-tree-participate">participates<a class="self-link" href="#concept-tree-participate"></a></dfn> in
+   <p>An object that <dfn data-dfn-for="tree" data-dfn-type="dfn" data-export="" data-lt="participate|participate in a tree|participates in a tree" id="concept-tree-participate">participates<a class="self-link" href="#concept-tree-participate"></a></dfn> in
 a <a data-link-type="dfn" href="#concept-tree">tree</a> has a <dfn data-dfn-for="tree" data-dfn-type="dfn" data-export="" id="concept-tree-parent">parent<a class="self-link" href="#concept-tree-parent"></a></dfn>, which is either another object
 or null, and an ordered list of zero or more <dfn data-dfn-for="tree" data-dfn-type="dfn" data-export="" data-lt="child|children" id="concept-tree-child">child<a class="self-link" href="#concept-tree-child"></a></dfn> objects. An object <var>A</var> whose <a data-link-type="dfn" href="#concept-tree-parent">parent</a> is object <var>B</var> is a <a data-link-type="dfn" href="#concept-tree-child">child</a> of <var>B</var>.</p>
    <p>The <dfn data-dfn-for="tree" data-dfn-type="dfn" data-export="" id="concept-tree-root">root<a class="self-link" href="#concept-tree-root"></a></dfn> of an object is itself, if its <a data-link-type="dfn" href="#concept-tree-parent">parent</a> is null, or else it is the <a data-link-type="dfn" href="#concept-tree-root">root</a> of its <a data-link-type="dfn" href="#concept-tree-parent">parent</a>. The <a data-link-type="dfn" href="#concept-tree-root">root</a> of a <a data-link-type="dfn" href="#concept-tree">tree</a> is any object <a data-link-type="dfn" href="#concept-tree-participate">participating</a> in that <a data-link-type="dfn" href="#concept-tree">tree</a> whose <a data-link-type="dfn" href="#concept-tree-parent">parent</a> is null. </p>
@@ -5063,6 +5063,7 @@ <h2 class="no-num heading settled" id="acks"><span class="content">Acknowledgmen
 James Graham,
 James Greene,
 James Robinson,
+Jeffrey Yasskin,
 Jens Lindström,
 Jesse McCarthy,
 João Eiras,
@@ -5706,6 +5707,8 @@ <h3 class="no-num no-ref heading settled" id="index-defined-here"><span class="c
    <li><a href="#dom-treewalker-parentnode">parentNode()</a><span>, in §6.2</span>
    <li><a href="#partially-contained">partially contained</a><span>, in §5.2</span>
    <li><a href="#concept-tree-participate">participate</a><span>, in §2.1</span>
+   <li><a href="#concept-tree-participate">participate in a tree</a><span>, in §2.1</span>
+   <li><a href="#concept-tree-participate">participates in a tree</a><span>, in §2.1</span>
    <li><a href="#dom-eventlisteneroptions-passive">passive</a><span>, in §3.6</span>
    <li><a href="#dom-nodeiterator-pointerbeforereferencenode">pointerBeforeReferenceNode</a><span>, in §6.1</span>
    <li><a href="#concept-range-bp-position">position</a><span>, in §5.2</span>