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.

archive/historic/index.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: archive/historic/README.md -->
 <h1 id="historic-archive-of-ioccc-winning-entries">Historic archive of IOCCC winning entries</h1>
 <h2 id="historic-archives-as-bz2-compressed-tarballs">Historic archives as bz2 compressed tarballs</h2>
 <p><strong>WARNING:</strong> These historic archives contain lots of code that will no longer compile,
@@ -222,6 +223,7 @@ done</code></pre>
         https://creativecommons.org/licenses/by-sa/4.0/
 
 -->
+<!-- AFTER: last line of markdown file: archive/historic/README.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 -->