Update index.html

fixes w3c/html-aria#94

html-aria/index.html

@@ -239,7 +239,7 @@ <h2 id="docconformance">Document conformance requirements for use of ARIA attrib
     </TR>
     <TR id="form" tabindex="-1">
       <TD><code><a href="https://w3c.github.io/html/sec-forms.html#the-form-element">form</a></code></TD>
-      <TD><code>role=<a href="#index-aria-form">form</a></code></TD>
+      <TD><code>role=<a href="#index-aria-form">form</a></code> if the <code><a href="https://w3c.github.io/html/sec-forms.html#the-form-element">form</a></code> element has an <a href="https://w3c.github.io/html-aam/#dfn-accessible-name" data-link-type="dfn">accessible name</a>. Otherwise, <a>no corresponding role</a>.</TD>
       <TD><p>Role: <a href="#index-aria-search"><code>search</code></a>, <code><a href="#index-aria-none">none</a></code> or <a href="#index-aria-presentation"><code>presentation</code></a></p>
         <p><a href="#index-aria-global">global <code>aria-*</code> attributes</a> and any <code>aria-*</code> attributes applicable to the allowed roles and implied role (if any)</p></TD>
     </TR>