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.

2005/toledo/README.md

@@ -1,20 +1,20 @@
 ## To build:
 
-```<!---sh-->
+``` <!---sh-->
     make
 ```
 
 
 ## To use:
 
-```<!---sh-->
+``` <!---sh-->
     ./toledo [a ...]
 ```
 
 
 ## Try:
 
-```<!---sh-->
+``` <!---sh-->
     ./toledo a
     ./toledo a b
 ```
@@ -30,7 +30,7 @@ Two alternate versions of this entry, [toledo2.c](toledo2.c) and
 
 To compile the alternate versions:
 
-```<!---sh-->
+``` <!---sh-->
     make alt
 ```
 
@@ -63,7 +63,7 @@ This is a [chess](https://en.wikipedia.org/wiki/Chess) program, it can work in
 two modes: two-players, and one player (always white) against the machine. To
 get the first mode, run the program without arguments:
 
-```<!---sh-->
+``` <!---sh-->
     ./toledo
 ```
 
@@ -71,14 +71,14 @@ The other mode is accessible running the program with one argument
 (5-[ply](https://en.wikipedia.org/wiki/Ply_(game_theory))
 analysis):
 
-```<!---sh-->
+``` <!---sh-->
     ./toledo a
 ```
 
 Two arguments for 6-[ply](https://en.wikipedia.org/wiki/Ply_(game_theory))
 analysis:
 
-```<!---sh-->
+``` <!---sh-->
     ./toledo a b
 ```