improved indentation and whitespace for markdown code blocks

All code blocks in markdown have been intended by at least 4 spaces.

We add `--tab-stop=8` to all `pandoc(1)` executions in order to set
a better tab stop indentation, especially for tab intended code blocks.

Changed `bin/pandoc-wrapper.sh` VERSION from "1.5.3 2024-03-26"
to "1.6 2024-03-31".

Fixed `1991/brnstnd/sorta.README.md` so that the sorta code
is code blocks.

Removed unneeded paragraph group in copyright in `inc/footer.default.html`.

Fixed excess whitespace after list Author on entry `index.html` page.

Changed `bin/output-index-author.sh` VERSION from "1.5.2 2024-03-26"
to "1.6 2024-03-31".

Performed `make www` to perform the above and test under macOS.

TODO: Fix the problem of the initial line of code being extra intended.
TODO: Fix excess whitespace around code that is inline.

2019/diels-grabsch1/README.md

@@ -1,21 +1,21 @@
 ## To build:
 
 ```sh
-make
+    make
 ```
 
 
 ## To use:
 
 ```sh
-./prog < file > file.Z
+    ./prog < file > file.Z
 ```
 
 
 ## Try:
 
 ```sh
-./try.sh
+    ./try.sh
 ```
 
 
@@ -38,20 +38,20 @@ compresses differently? The judges know. :)
 #### Usage:
 
 ```sh
-./prog < input.txt > input.txt.Z
+    ./prog < input.txt > input.txt.Z
 ```
 
 #### Example:
 
 ```sh
-./prog < guidelines.txt > guidelines.txt.Z
+    ./prog < guidelines.txt > guidelines.txt.Z
 ```
 
 #### Check for correctness:
 
 ```sh
-zcat guidelines.txt.Z > guidelines2.txt
-diff -s guidelines.txt guidelines2.txt
+    zcat guidelines.txt.Z > guidelines2.txt
+    diff -s guidelines.txt guidelines2.txt
 ```
 
 Of course you can  also use [2015/mills2](../../2015/mills2/mills2.c) instead of