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.

1996/westley/README.md

@@ -1,6 +1,6 @@
 ## To build:
 
-```<!---sh-->
+``` <!---sh-->
     make all
     ```
 
@@ -11,7 +11,7 @@
 
 ## To use:
 
-```<!---sh-->
+``` <!---sh-->
     ./clock1.sh
     ./clock2.sh
     ./clock3.sh
@@ -20,7 +20,7 @@
 
 ## Try:
 
-```<!---sh-->
+``` <!---sh-->
     ./try.sh
 ```
 
@@ -34,14 +34,14 @@ provided, to show the differences.
 
 ### Alternate build:
 
-```<!---sh-->
+``` <!---sh-->
     make alt
 ```
 
 
 ### Alternate try:
 
-```<!---sh-->
+``` <!---sh-->
     ./try.alt.sh
 ```
 
@@ -81,7 +81,7 @@ larger.
 
 The code is simple; the arguments passed are:
 
-```<!---sh-->
+``` <!---sh-->
     ./westley minute_map hour_map hand_symbol clock_image
 ```