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.

1995/index.html

@@ -168,8 +168,8 @@ ways.</p>
 <p>Please send us comments and suggestions what we have expressed above.
 Also include anything else that you would like to see in future contests.
 Send such email to:</p>
-<pre><code>...!{sun,pacbell,uunet,pyramid}!hoptoad!judges
-judges@toad.com</code></pre>
+<pre><code>    ...!{sun,pacbell,uunet,pyramid}!hoptoad!judges
+    judges@toad.com</code></pre>
 <p>If you use, distribute or publish these entries in some way, please drop
 us a line. We enjoy seeing who, where and how the contest is used.</p>
 <h2 id="final-comments">Final Comments</h2>