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/boutines/README.md

@@ -1,6 +1,6 @@
 ## To build:
 
-```<!---sh-->
+``` <!---sh-->
     make
 ```
 
@@ -15,20 +15,20 @@ require it?](../../faq.html#imagemagick).
 Look here to find some [SVG Viewer
 Implementations](https://www.w3.org/Graphics/SVG/WG/wiki/Implementations).
 
-```<!---sh-->
+``` <!---sh-->
     ./boutines < input > output.svg
 ```
 
 
 ## Try:
 
-```<!---sh-->
+``` <!---sh-->
     ./try.sh
 ```
 
 If `ruby` is installed [try.sh](try.sh) will generate an SVG file by:
 
-```<!---sh-->
+``` <!---sh-->
     ruby -e '20.times{puts "#{rand} #{rand}"}' | ./boutines > test.svg
 ```
 
@@ -75,7 +75,7 @@ an [SVG](https://www.w3.org/TR/SVG11/expanded-toc.html) stream.
 
 This will possibly save a compressed SVG file and may be useful:
 
-```<!---sh-->
+``` <!---sh-->
     ./boutines | gzip > result.svg.gz
 ```