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.

2011/goren/README.md

@@ -1,20 +1,20 @@
 ## To build:
 
-```<!---sh-->
+``` <!---sh-->
     make
 ```
 
 
 ## To use:
 
-```<!---sh-->
+``` <!---sh-->
     echo "some text" | ./goren
 ```
 
 
 ## Try:
 
-```<!---sh-->
+``` <!---sh-->
     ./try.sh
 ```
 
@@ -27,13 +27,13 @@ In the words of [René François Ghislain Magritte Magritte](http://en.wikipedia
 
 One may ask the surrealist question:
 
-```<!---sh-->
+``` <!---sh-->
     echo 'If | is just a representation of a pipe, then how can data stuff it?' | ./goren
 ```
 
 However if one takes a firm stand and declares:
 
-```<!---sh-->
+``` <!---sh-->
     echo '| is just a representation of a pipe because I say so! So stuff it!' | ./goren
 ```