add note about HiKey and HiKey 960

static/faq.html

@@ -326,6 +326,15 @@
                         <li>Nexus 5 (hammerhead)</li>
                         <li>Samsung Galaxy S4 (jflte)</li>
                     </ul>
+
+                    <p>GrapheneOS also used to provide official source-level support for the
+                    following development boards but dropped support due to lack of community
+                    interest and lack of hardware availability:</p>
+
+                    <ul>
+                        <li>HiKey 960 (hikey960)</li>
+                        <li>HiKey (hikey)</li>
+                    </ul>
                 </article>
             </section>