Clarify hash expression format for digestSRI.

Author: msporny

index.html

@@ -3177,7 +3177,10 @@ <h2>Integrity of Related Resources</h2>
                 <tr>
                   <td>`digestSRI`</td>
                   <td>
-One or more cryptographic digests, as defined in [[[SRI]]].
+One or more cryptographic digests, as defined by the `hash-expression` ABNF
+grammar defined in the [[[SRI]]] specification,
+<a data-cite="SRI#the-integrity-attribute">Section 3.5: The `integrity`
+attribute</a>.
                   </td>
                 </tr>
               </tbody>