set pandoc 8 character tab stops for HTML conversion

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 "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`.

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

1990/theorem/index.html

@@ -165,7 +165,7 @@ numerically solves the equation <code>y'=f(x,y)</code>, with a step size of <cod
 usage), over the interval <code>x=[x1,x2]</code>, with the initial condition of <code>y(x1)=y1</code>.</p>
 <p>The ‘expression’ <code>f(x,y)</code> is any function of <code>x</code> and <code>y</code> with the
 operators:</p>
-<pre><code>+   -   *   /   ^</code></pre>
+<pre><code>+       -       *       /       ^</code></pre>
 <p>The symbol <code>^</code> is the power operator. Note that it only supports
 integer powers. Also note that all expressions are evaluated strictly
 left to right. (i.e., parenthesis aren’t supported).</p>
@@ -213,11 +213,11 @@ lines, each less than 99 characters long.</p>
 
     You are free to share and adapt this file under the terms of this license:
 
-    Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
+        Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
 
     For more information, see:
 
-    https://creativecommons.org/licenses/by-sa/4.0/
+        https://creativecommons.org/licenses/by-sa/4.0/
 
 -->
 
@@ -280,7 +280,7 @@ lines, each less than 99 characters long.</p>
 <div class="footer">
   <h2>Copyright and CC BY-SA 4.0 License</h2>
   <p>This file and web page is:</p>
-  <blockquote><p><b>Copyright &copy; 1984-2024 by Landon Curt Noll. All Rights Reserved.</b></p></blockquote>
+  <blockquote><b>Copyright &copy; 1984-2024 by Landon Curt Noll. All Rights Reserved.</b></blockquote>
   <p>You are free to share and adapt this file under the terms of this license:</p>
   <blockquote><b>Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)</b></blockquote>
   <p>For more information, see:</p>