improve topbar

The icons used to show the menu open (`png/hamburger-icon-open.png`)
and closed (`png/hamburger-icon-closed.png`) have been added.

Changed `inc/topbar.default.html` to use the png icons instead
of a svg file.

A new page `nojs-menu.html` has been added for when
JavaScript is disabled.

Changed `bin/gen-top-html.sh` VERSION from to "1.4.4 2024-04-21"
to "1.4.5 2024-04-23".

Sorted top sections in `inc/md2html.cfg` and added
a section for `nojs-menu.md`.

Fixed `ioccc.css` so that the topbar and related pulldown
menus had the correct background colour.

Ran `make www` to perform the above.

TODO: Detect when JavaScript is disabled and display:

		Please
		Enable
	      JavaScript

      As a link to the new `nojs-menu.html` page.

TODO: Fix a problem on wide screens where some of
      the righthand edge pulldown menus are cutoff.

TODO: Fix the 5 HTML 5 errors introduced by the topbar code.

nojs-menu.md

@@ -0,0 +1,29 @@
+#### Here is the menu you missed because JavaScript is disabled:
+
+## Entries
+
+* [Winning Entries](%%DOCROOT_SLASH%%years.html)
+* [People who have won](%%DOCROOT_SLASH%%authors.html)
+* [Location of authors](%%DOCROOT_SLASH%%location.html)
+* [Bugs & (Mis)features](%%DOCROOT_SLASH%%bugs.html)
+
+## Status
+
+* [IOCCC News](%%DOCROOT_SLASH%%news.html)
+* [Contest status](%%DOCROOT_SLASH%%status.html)
+* [Rules & Guidelines](%%DOCROOT_SLASH%%next/index.html)
+
+## FAQ
+
+* [FAQ](%%DOCROOT_SLASH%%faq.html)
+* [How to enter the IOCCC](%%DOCROOT_SLASH%%faq.html#fix_an_entry)
+* [Fixing IOCCC entries](%%DOCROOT_SLASH%%faq.html#fix_an_entry)
+* [Fixing the web site](%%DOCROOT_SLASH%%faq.html#fix_web_site)
+* [Fixing author info](%%DOCROOT_SLASH%%faq.html#fix_author)
+
+## About
+
+* [IOCCC Home](%%DOCROOT_SLASH%%index.html)
+* [The IOCCC Judges](%%DOCROOT_SLASH%%contact.html)
+* [Contacting the IOCCC](%%DOCROOT_SLASH%%contact.html)
+* [Thanks for the help](%%DOCROOT_SLASH%%thanks-for-help.html)