Typo fix in SECURITY.md

Also removed what seems to be unnecessary quotes, much along the lines
in some FAQ links (that will be having the quotes removed).

Added SECURITY.md to bin/md2html.cfg and updated bin/gen-top-html.sh to
build SECURITY.html. The configuration can be improved for keywords and
other things and the file is not linked into the website either but
presumably it should be.

SECURITY.md

@@ -9,6 +9,6 @@ Use code in this repo at your own risk!  We will **NOT** provide security update
 ## Reporting a Vulnerability
 
 Even though **ALL IOCCC ENTRY CODE IS UNSUPPORTED**,
-if you wish to discuss a security concen regarding this repo then
+if you wish to discuss a security concern regarding this repo then
 please **send email the IOCCC judges** by consulting the bottom section
-of the "[How to contact the IOCCC](https://www.ioccc.org/contact.html)" web page.
+of the [How to contact the IOCCC](https://www.ioccc.org/contact.html) web page.