add hack-a-round for language specified markdown code blocks

When language is specified in a markdown code block such as:

````
```c
    printf("Hello, world!\n");
```
````

is used, the resulting HTML as produced by `pandoc(1)` combined
with our revised `ioccc.css` is not intent the code block well.

A temporary "_hack-a-round_" is to turn the "markdown code language
specifier" into an HTML comment.  For example:

````
```<!---c-->
    printf("Hello, world!\n");
```
````

This commits turns off existing markdown code language specifiers
for now, while preserving our ability to restore them in the future
when a better  "_hack-a-round_" to the "markdown code language
specifier" problem is found.

The HTML impact if this "_hack-a-round_" is to produce HTML that
looks like this:

```
<pre class="&lt;!---c--&gt;"><code> .. </code></pre>
```

We might be able to create a complex set of classes for each markdown
code language (there won't be very many) in `ioccc.css`, or we might
find a more general CSS (or maybe `pandoc(1)`?) solution.

For now, this hack-a-round will have to do.

1993/jonth/README.md

@@ -5,14 +5,14 @@ compile. macOS users running Mountain Lion and later will need to download and
 install [XQuartz](https://www.xquartz.org) in order to compile and run this
 entry.
 
-```sh
+```<!---sh-->
     make all
 ```
 
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./jonth	# must be run on an X11 server
 ```
 

1993/jonth/index.html

@@ -145,9 +145,9 @@ Location: <a href="../../location.html#NO">NO</a> - <em>Kingdom of Norway</em> (
 compile. macOS users running Mountain Lion and later will need to download and
 install <a href="https://www.xquartz.org">XQuartz</a> in order to compile and run this
 entry.</p>
-<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a>    <span class="fu">make</span> all</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make all</code></pre>
 <h2 id="to-use">To use:</h2>
-<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./jonth</span>     <span class="co"># must be run on an X11 server</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./jonth     # must be run on an X11 server</code></pre>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
 <p>Use <code>h</code> and <code>l</code> to shift objects left or right. Use <code>k</code> to
 rotate and press SPACE to drop.</p>