Important fixes in 2020/ferguson2

A typo in markdown meant that a link was not formed.

Renamed enigma.html to enigma.txt. Although it was to be set to viewed
as text the problem is that as a html file running a linter on it will
cause errors (obviously).

The .entry.json and all files that referred to the file enigma.html (not
in remote web servers, obviously, but just this website) now refer to
enigma.txt, except that enigma.html was now added to .gitignore and the
recode.md (in the example command) redirects to enigma.html as that
should be a html file, assuming they have the right key (of the
selection I gave).

These problems were not discovered due to trying to get the html files
in a good state (ironically) and knowing that I had written a lot.

I believe now that the files should be okay.

Although I did use sgit I did it carefully and I still ran make
quick-readme2index and make gen_other_html.

2020/ferguson2/recode.html

@@ -876,7 +876,7 @@ shouldn’t this entry include something that is fun too? But if that’s the ca
 why on Earth should it be unscrambled? It would be more fun and a great way to
 explore this entry if you have to use the Enigma machine to read the message!</p>
 <p>So this is what I offer: if you take one of the settings below and run the
-Enigma machine simulator on the file [enigma.html][enigma.html] you will
+Enigma machine simulator on the file <a href="enigma.txt">enigma.txt</a> you will
 unlock a html file with something special in it. I recommend you decrypt it to
 <code>decrypted.html</code> and open it in a web browser.</p>
 <p>The correct settings is listed below but <em>you</em> must determine which one is the
@@ -919,8 +919,8 @@ think that I would give too much away? :)</p>
 the key you wish to select is</p>
 <pre><code>    0EZ4PC1CC0PGTAQSOXWNMDRYKFUZEI</code></pre>
 <p>you can do:</p>
-<pre><code>    ./recode -R0EZ4PC1CC0PGTAQSOXWNMDRYKFUZEI -fenigma.html | ./prog - 2&gt;/dev/null &gt; enigma.deciphered.html</code></pre>
-<p>Then open <code>enigma.deciphered.html</code> in your browser. A command is provided in
+<pre><code>    ./recode -R0EZ4PC1CC0PGTAQSOXWNMDRYKFUZEI -fenigma.txt | ./prog - 2&gt;/dev/null &gt; enigma.html</code></pre>
+<p>Then open <code>enigma.html</code> in your browser. A command is provided in
 <a href="testing-procedure.html">testing-procedure.html</a> that does this too but it
 shows how you can use a file as input for the key instead as well as how I
 tested the code.</p>