fix HTML problems associated with leading ---'s

Please do not use "**---**" in markdown lines to separate sections.

This causes `pandoc(1)` to generate "**\<hr />**".

The "**\<hr />**" has no effect in standard HTML 5 and interacts
badly with unquoted attribute values.

If a horizontal line is really needed, use "**\<hr>**".

If a short line is needed, use: "**\<hr
style="width:10%;text-align:left;margin-left:0">**"

2020/kurdyukov4/README.md

@@ -36,7 +36,7 @@ way it works too fast regardless of the context length, and it's much less fun.
 
 The author wrote in reply:
 
----
+<hr style="width:10%;text-align:left;margin-left:0">
 
 Wow, amazing! Very fast, but there is a drawback to randomness.
 If some string only appears after half the input, the first instance
@@ -56,7 +56,7 @@ Example:
     -- Author
 ```
 
----
+<hr style="width:10%;text-align:left;margin-left:0">
 
 
 Try using the same random seed and varying the context size.

2020/kurdyukov4/index.html

@@ -167,7 +167,7 @@ context length decreases:</p>
 the (still non-standard, for some reason) library function <code>memmem()</code>, but that
 way it works too fast regardless of the context length, and it’s much less fun.</p>
 <p>The author wrote in reply:</p>
-<hr />
+<hr style="width:10%;text-align:left;margin-left:0">
 <p>Wow, amazing! Very fast, but there is a drawback to randomness.
 If some string only appears after half the input, the first instance
 of this string will have a 50% chance of occurrence.
@@ -179,7 +179,7 @@ Example:</p>
     # more ones in output</code></pre>
 <pre><code>    But this will happen very rarely on real data.
     -- Author</code></pre>
-<hr />
+<hr style="width:10%;text-align:left;margin-left:0">
 <p>Try using the same random seed and varying the context size.</p>
 <p>BTW: what on Middle-earth is <code>lámatyávë</code>? It’s Quenya, one of the languages of
 the Elves in Tolkien’s Legendarium. It means sound taste (plural is lámatyáver)