Ensure that /snapshot is always "up-to date"

html/index.html

@@ -16,6 +16,9 @@
 			<ul>
 				<li>Get a high-resolution snapshot image from the server.</li>
 				<li>Uses resolution specified by <i>-camera-snapshot.height=</i>.</li>
+				<br>
+				<li><a href="snapshot?max_delay=0">/snapshot?max_delay=0</a> to get a snapshot captured exactly now.</li>
+				<li><a href="snapshot?max_delay=300">/snapshot?max_delay=300</a> (default) to get a cached snapshot captured up-to 300 ms in the past.</li>
 			</ul>
 		</li>
 		<br>