Add telnet server

templates/about.html

@@ -34,6 +34,13 @@
             like. The usage is explained in more detail in the <a
                     href="https://git.ianrenton.com/ian/spothole/src/branch/main/README.md">README file</a>.
         </li>
+        {% if telnet_server_enabled %}
+        <li>You can use it as a traditional telnet-based source of spots, similar to DXSpider and other software, <b>in
+            your desktop logging application</b>. To do this, set up your logger with the server address
+            <code>{{ telnet_server_address }}</code> and port <code>{{ telnet_server_port }}</code>. You can also access
+            it from a terminal with <code>telnet {{ telnet_server_address }} {{ telnet_server_port }}</code>.
+        </li>
+        {% end %}
         <li>You can <b>write your own client using the Spothole API</b>, using the main Spothole instance to provide
             data, and do whatever you like with it. The README contains guidance on how to do this, and the full API
             docs are linked above. You can also find reference implementations in the form of Spothole's own web-based
@@ -85,7 +92,8 @@
     <p>Spothole can retrieve alerts from: <a href="https://www.ng3k.com/">NG3K</a>, <a href="https://pota.app">POTA</a>,
         <a href="https://www.sota.org.uk/">SOTA</a>, <a href="https://wwff.co/">WWFF</a>, <a
                 href="https://www.parksnpeaks.org/">Parks 'n' Peaks</a>, <a href="https://www.wota.org.uk/">WOTA</a> and
-        <a href="https://www.beachesontheair.com/">BOTA</a>.</p>
+        <a href="https://www.beachesontheair.com/">BOTA</a>. It also fetches contest dates from
+        <a href="https://contestcalendar.com/">WA7BNM Contest Calendar</a> and RSGB contest calendars.</p>
     <p>Spothole can retrieve solar and propagation condition data from <a href="https://www.hamqsl.com">HamQSL</a>, the
         <a href="https://www.swpc.noaa.gov/">NOAA Space Weather Prediction Center</a>, the <a
                 href="https://giro.uml.edu/">Lowell GIRO Data Center</a> and <a href="https://prop.kc2g.com/">prop.kc2g.com</a>
@@ -162,6 +170,10 @@
         modify it however you like, you can claim you wrote it and charge people £1000 for a copy, I don't really mind.
         (Please don't do the last one. But if you're using my code for something cool, it would be nice to hear from
         you!)</p>
+    <h4 class="mt-4">What commands are supported in the telnet server?</h4>
+    <p>Currently, <code>exit</code>, and nothing else. Support for some DXSpider-like commands may be added to Spothole
+        in due course, but at the moment if you want to add Spothole as a telnet cluster data source to your desktop
+        logging application, that application must handle filtering itself.</p>
     <h2 id="accuracy" class="mt-4">Data Accuracy</h2>
     <p>Please note that the data coming out of Spothole is only as good as the data going in. People mis-hear and make
         typos when spotting callsigns all the time. There are also plenty of cases where Spothole's data, particularly