Update External Sends docs for 7.1

include/external-sends.html

@@ -7,12 +7,14 @@
   is a one-way signal routing that leaves all existing signal processing
   just as it was.
 </p>
+
 <p>
   Most people will not have much use for this, but it can be useful to experiment
   with external applications or hardware signal processing applications.
 </p>
 
 <h2>Adding an External Send</h2>
+
 <p>
   Context-clicking on the
   <a href="@@processor-box">processor box</a> in a
@@ -23,7 +25,9 @@
 </p>
 
 <h2>Removing an External Send</h2>
+
 <p>An external send can be removed in several ways:</p>
+
 <ul>
 <li><kbd class="mouse mod3">Right</kbd>-clicking the send in the processor box and
   choosing either <kbd class="menu">Cut</kbd> or <kbd class="menu">Delete</kbd>.</li>
@@ -32,6 +36,7 @@
 </ul>
 
 <h2>Altering Send Levels</h2>
+
 <p>
   Just below the send in the processor box is a small fader that can be used
   like all other faders in Ardour to control the gain applied to the signal
@@ -45,8 +50,18 @@
   it on and off. When turned off, silence will be delivered to the send. When
   turned on, the signal within the channel strip will be delivered.
 </p>
+
 <h2>Editing Send Routing</h2>
+
 <p>
   Double-clicking on the send in the processor box will re-display the patchbay
-  dialog that gives full control over the routing of the send.
+  dialog that gives full control over the routing of the send, as well as
+  additional controls: gain fader, panner, signal meter, and phase inverter.
 </p>
+
+<figure class="right">
+  <img src="/images/external-send-dialog.png" width="50%" alt="External Send Dialog">
+  <figcaption>
+    External Send Dialog
+  </figcaption>
+</figure>