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/index.html

@@ -150,9 +150,9 @@ vocabulary!</p>
 <pre><code>[1991/davidguy](../years.html#1991_davidguy)
 [2011/blakely](../years.html#2011_blakely)</code></pre>
 <p>These nods to not run afoul of the guideline:</p>
-<pre><code>We tend to dislike programs that:
-...
-are rather similar to previous entries</code></pre>
+<pre><code>    We tend to dislike programs that:
+    ...
+    are rather similar to previous entries</code></pre>
 <p>because the entry <a href="2019/dogon/index.html">2019/dogon</a> appropriately pays homage
 to past entries without blatantly reusing their code.</p>
 <p>…We’ll stop spouting spoilers now. Have fun exploring all the entries!</p>