fix markdown footnote problem caused by pandoc

Add "<!-- BEFORE: 1st line of markdown file: FILE/PATH -->"
before the markdown content.  This line appears in the
generated HTML.

Add "<!-- AFTER: last line of markdown file: FILE/PATH -->"
after the markdown content.  This line appears in the
generated HTML.

We test a fix relating to problems produced by `pandoc(1)`
when footnotes are added at the end of generated HTML.
This test is made for `2000/bmeyer/index.html`.

Fixed exit 4 in `bin/md2html.sh that should be exit 5.

Changed `bin/md2html.sh` VERSION from to "1.3 2024-04-14"
to "1.4 2024-04-18".

Run `bin/readme2index.sh -v 1 2000/bmeyer` to perform the above.

years.html

@@ -132,6 +132,7 @@
 <!-- END: this line ends content from: inc/before-content.default.html -->
 <!-- START: this line starts content for HTML phase 21 by: bin/pandoc-wrapper.sh via bin/md2html.sh -->
 
+<!-- BEFORE: 1st line of markdown file: .gen-years.sh.43687.years.md -->
 <h1 id="ioccc-winning-entries-by-year">IOCCC Winning Entries by Year</h1>
 <h3 id="jump-to">Jump to:</h3>
 <p><a href="#2020">2020</a> | <a href="#2019">2019</a> | <a href="#2018">2018</a> | <a href="#2015">2015</a> | <a href="#2014">2014</a> | <a href="#2013">2013</a> | <a href="#2012">2012</a> | <a href="#2011">2011</a><br><br>
@@ -711,6 +712,7 @@
 <li>Download all <a href="1984/1984.tar.bz2">1984 IOCCC entry source</a><br></li>
 </ul>
 <p> <strong>Jump to:</strong> <a href="#">top</a></p>
+<!-- AFTER: last line of markdown file: .gen-years.sh.43687.years.md -->
 
 <!-- END: this line ends content for HTML phase 21 by: bin/pandoc-wrapper.sh via bin/md2html.sh -->
 <!-- START: this line starts content from: inc/after-content.default.html -->