add a place-holder link for the hour-long video

R=rsc
CC=go-dev
http://go/go-review/1017054

lib/godoc/godoc.html

@@ -86,6 +86,7 @@
     <li><a href="/doc/go_faq.html" class="noline">FAQ</a></li>
     <li><a href="/doc/go_lang_faq.html" class="noline">Language Design FAQ</a></li>
     <li><a href="/doc/go_for_cpp_programmers.html" class="noline">Go for C++ Programmers</a></li>
+    <li><a href="XXX" class="noline">Tech talk (1 hour)</a></li>
 
     <li class="blank">&nbsp;</li>
     <li class="navhead">How To</li>