improve how markdown code language is commented

We added a space between the markdown triple code mark
and language that was enclosed in HTML comments.

So a line of the form:

````
```<!---c--->
````

became:

````
``` <!---c--->
````

This was done to **help** some code see that the HTML comment
string was not a markdown code specifier.   Not all code
understands this after this changed.  For example, `pandoc(1)`
still forms HTML classes of the form "&lt;!---c--&gt;"
when it encounters the above mentioned change.

We also fixed a problem with `2019/dogon/README.md` regarding
a markdown code block.

We also fixed a problem with `2020/yang/README.md` regarding
a markdown code block.

2020/yang/README.md

@@ -1,20 +1,20 @@
 ## To build:
 
-```<!---<!---sh-->-->
+``` <!---sh-->
     make
 ```
 
 
 ## To use:
 
-```<!---<!---sh-->-->
+``` <!---sh-->
     ./prog [PIN] < input.txt > output.c
 ```
 
 
 ## Try:
 
-```<!---<!---sh-->-->
+``` <!---sh-->
     ./try.sh
 ```
 
@@ -22,7 +22,7 @@
 The author provided the file [cppp.cc](cppp.cc) which can preprocess the
 generated output to make them more acceptable to typical compilers. To build:
 
-```<!---<!---sh-->-->
+``` <!---sh-->
     make cppp
 ```
 
@@ -44,7 +44,7 @@ spoiler](spoiler.html) that shows how this entry was written.
 
 ### Synopsis
 
-```<!---<!---sh-->-->
+``` <!---sh-->
     echo "Hello world" | ./prog 12345 > encoded.c
 
     gcc -DPIN=12345 encoded.c -o ./decoded && ./decoded
@@ -63,14 +63,14 @@ Mile is a C code generator.  Run without arguments for the help message below:
 When run with an encoding PIN (first command line argument), Mile will
 read bytes from `stdin` and generate C code on `stdout`.  Example:
 
-```<!---<!---sh-->-->
+``` <!---sh-->
     echo "Hello, world!" | ./prog 56789 > encoded.c
 ```
 
 This generated code will reproduce the same input bytes on `stdout` when
 executed, if it was compiled with the same encoding PIN.
 
-```<!---<!---sh-->-->
+``` <!---sh-->
     gcc -DPIN=56789 encoded.c -o decoded
 ```
 

2020/yang/index.html

@@ -141,14 +141,14 @@ Location: <a href="../../location.html#US">US</a> - <em>United States of America
 <!-- START: this line starts content for HTML phase 21 by: bin/pandoc-wrapper.sh via bin/md2html.sh -->
 
 <h2 id="to-build">To build:</h2>
-<pre class="&lt;!---&lt;!---sh--&gt;--&gt;"><code>    make</code></pre>
+<pre class="&lt;!---sh--&gt;"><code>    make</code></pre>
 <h2 id="to-use">To use:</h2>
-<pre class="&lt;!---&lt;!---sh--&gt;--&gt;"><code>    ./prog [PIN] &lt; input.txt &gt; output.c</code></pre>
+<pre class="&lt;!---sh--&gt;"><code>    ./prog [PIN] &lt; input.txt &gt; output.c</code></pre>
 <h2 id="try">Try:</h2>
-<pre class="&lt;!---&lt;!---sh--&gt;--&gt;"><code>    ./try.sh</code></pre>
+<pre class="&lt;!---sh--&gt;"><code>    ./try.sh</code></pre>
 <p>The author provided the file <a href="cppp.cc">cppp.cc</a> which can preprocess the
 generated output to make them more acceptable to typical compilers. To build:</p>
-<pre class="&lt;!---&lt;!---sh--&gt;--&gt;"><code>    make cppp</code></pre>
+<pre class="&lt;!---sh--&gt;"><code>    make cppp</code></pre>
 <p>See the author’s remarks for more details.</p>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
 <p>You might think of this entry as code obfuscater with a code.
@@ -159,7 +159,7 @@ What is compiling this entry about?
 spoiler</a> that shows how this entry was written.</p>
 <h2 id="authors-remarks">Author’s remarks:</h2>
 <h3 id="synopsis">Synopsis</h3>
-<pre class="&lt;!---&lt;!---sh--&gt;--&gt;"><code>    echo &quot;Hello world&quot; | ./prog 12345 &gt; encoded.c
+<pre class="&lt;!---sh--&gt;"><code>    echo &quot;Hello world&quot; | ./prog 12345 &gt; encoded.c
 
     gcc -DPIN=12345 encoded.c -o ./decoded &amp;&amp; ./decoded</code></pre>
 <h3 id="details">Details</h3>
@@ -169,10 +169,10 @@ spoiler</a> that shows how this entry was written.</p>
     where [PIN] is an integer in the range of 1..65535</code></pre>
 <p>When run with an encoding PIN (first command line argument), Mile will
 read bytes from <code>stdin</code> and generate C code on <code>stdout</code>. Example:</p>
-<pre class="&lt;!---&lt;!---sh--&gt;--&gt;"><code>    echo &quot;Hello, world!&quot; | ./prog 56789 &gt; encoded.c</code></pre>
+<pre class="&lt;!---sh--&gt;"><code>    echo &quot;Hello, world!&quot; | ./prog 56789 &gt; encoded.c</code></pre>
 <p>This generated code will reproduce the same input bytes on <code>stdout</code> when
 executed, if it was compiled with the same encoding PIN.</p>
-<pre class="&lt;!---&lt;!---sh--&gt;--&gt;"><code>    gcc -DPIN=56789 encoded.c -o decoded</code></pre>
+<pre class="&lt;!---sh--&gt;"><code>    gcc -DPIN=56789 encoded.c -o decoded</code></pre>
 <p>The generated code reconstructs all data at compile time by seeding a
 random number generator with the given PIN to reproduce the input bytes,
 and simply does one <code>fwrite(3)</code> call at run time to print those bytes. Not