[doc] add a link h2olog in "Key Features"
@@ -40,6 +40,7 @@ Explanation of the benchmark charts can be found in the <a href="benchmarks.html
<li><a href="configure/proxy_directives.html">reverse proxy</a>
<li><a href="configure/mruby.html">scriptable using mruby</a> (Rack-based)
<li>graceful restart and self-upgrade
+<li><a href="configure/h2olog.html">BPF-based tracing tool</a> (experimental)</li>
</ul>
? })
