[css-transitions-2] Make id ref for DOM interfaces section consistent with animations

Author: birtles

css-transitions-2/Overview.bs

@@ -148,7 +148,7 @@ to the <a>global animation list</a> at the moment they are constructed.
 			</ul>
 	</dl>
 
-# DOM Interfaces # {#DOM-interfaces}
+# DOM Interfaces # {#interface-dom}
 
 ## The CSSTransition interface ## {#the-CSSTransition-interface}
 

css-transitions-2/Overview.html

@@ -177,7 +177,7 @@ <h2 class="no-num no-toc no-ref heading settled" id="contents"><span class="cont
       <li><a href="#transition-event-types"><span class="secno">3.1</span> <span class="content">Types of <code>TransitionEvent</code></span></a>
      </ul>
     <li>
-     <a href="#DOM-interfaces"><span class="secno">4</span> <span class="content">DOM Interfaces</span></a>
+     <a href="#interface-dom"><span class="secno">4</span> <span class="content">DOM Interfaces</span></a>
      <ul class="toc">
       <li><a href="#the-CSSTransition-interface"><span class="secno">4.1</span> <span class="content">The CSSTransition interface</span></a>
      </ul>
@@ -306,7 +306,7 @@ <h3 class="heading settled" data-level="3.1" id="transition-event-types"><span c
       <li>Context Info: propertyName, elapsedTime, pseudoElement
      </ul>
    </dl>
-   <h2 class="heading settled" data-level="4" id="DOM-interfaces"><span class="secno">4. </span><span class="content">DOM Interfaces</span><a class="self-link" href="#DOM-interfaces"></a></h2>
+   <h2 class="heading settled" data-level="4" id="interface-dom"><span class="secno">4. </span><span class="content">DOM Interfaces</span><a class="self-link" href="#interface-dom"></a></h2>
    <h3 class="heading settled" data-level="4.1" id="the-CSSTransition-interface"><span class="secno">4.1. </span><span class="content">The CSSTransition interface</span><a class="self-link" href="#the-CSSTransition-interface"></a></h3>
 <pre class="idl">interface <dfn class="idl-code" data-dfn-type="interface" data-export="" id="csstransition">CSSTransition<a class="self-link" href="#csstransition"></a></dfn> : <a data-link-type="idl-name" href="https://w3c.github.io/web-animations/#animation">Animation</a> {
   readonly attribute DOMString <a class="idl-code" data-link-type="attribute" data-readonly="" data-type="DOMString " href="#dom-csstransition-transitionproperty">transitionProperty</a>;