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.

2014/sinon/README.md

@@ -1,13 +1,13 @@
 ## To build:
 
-```<!---sh-->
+``` <!---sh-->
     make
 ```
 
 
 ## To use:
 
-```<!---sh-->
+``` <!---sh-->
     ./hecate.sh
 
     ./glock.sh
@@ -16,7 +16,7 @@
 
 ## Try:
 
-```<!---sh-->
+``` <!---sh-->
     ./try.sh
 ```
 
@@ -41,7 +41,7 @@ under one minute.
 To start, compile and run the program.  To resume, compile and run the
 output repeatedly until you have won/lost the game.  For example:
 
-```<!---sh-->
+``` <!---sh-->
     cp prog.c run.c
     gcc -O0 run.c -o run && ./run | tee run.c
     gcc -O2 run.c -o run && ./run | tee run.c
@@ -106,7 +106,7 @@ a primary input.
 that there are no files named "run" and "run.c" in current directory
 (they will be overwritten) and run:
 
-```<!---sh-->
+``` <!---sh-->
     perl prog.c | bash
 ```