Additional fixes to the html.sed script

It now translates the characters '|' (pipe), '=' (equals) and '%'
(percent).

Checks were added in md2html.sh in the -s token=value so that token
cannot contain an = (equal), | (pipe) or a % (percent) and the value
cannot contain a | (pipe).

The reason that we cannot disallow a ';' or '&' is because the html
entities use those characters so if the sed script were to translate the
problematic characters it would cause a problem in the script.

Ran make www which updated 1988/robison/index.html and
1990/theorem/index.html.

1986/bright/README.md was fixed with the number of blank lines between
sections.

bin/html.sed

@@ -1,6 +1,6 @@
 #!/usr/bin/env sed
 #
-# bin/html.sed - translate certain characters to HTML & entities
+# html.sed - translate certain characters to HTML & entities
 #
 # This script was written in 2024 November by:
 #
@@ -11,10 +11,10 @@
 # "Because sometimes even the IOCCC Judges need some help." :-)
 #
 # This script will take certain characters, for instance '<', and convert them
-# to their respective html entity, for instance '&lt;', so that html lints do
+# to their respective HTML entity, for instance '&lt;', so that HTML lints do
 # not complain.
 #
-# For a list of the other html entities, should others be needed, see:
+# For a list of the other HTML entities, should others be needed, see:
 #
 #       https://www.w3schools.com/html/html_entities.asp
 #
@@ -26,7 +26,7 @@
 #
 #	sed -i -f bin/html.sed file
 #
-# VERSION="1.0 2024-11-04"
+# VERSION="1.1 2024-11-07"
 
 # IMPORTANT NOTE: the '&amp;' substitution MUST come first! This is because the
 # other substitutions have '&'s in them and if the '&amp;' came after it would
@@ -34,3 +34,6 @@
 s/&/\\\&amp;/g
 s/</\\\&lt;/g
 s/>/\\\&gt;/g
+s/|/\\\&verbar;/g
+s/=/\\\&equals;/g
+s/%/\\\&percnt;/g