fix more broken markdown links

We fix more markdown links in markdown files that refer to files
internally to the web site.

Added tmp tools to find and print various markdown links:

* `tmp/md-links.sh` - print all markdown links
* `tmp/md-token-links.sh` - print all markdown links that start with a **%%TOKEN%%**
* `tmp/md-local-links.sh` - print all markdown links to a local file
* `tmp/md-link-paths.sh` - print local file paths referenced in markdown links

Fixed a number of markdown formatting problems with `thanks-for-help.md`.
Fixed markdown links to files in `thanks-for-help.md`.  Improved
heading levels in `thanks-for-help.md`, and made entry sections consistent.

Changed all markdown links that end in "))" to end in a better way.

Explained in `markdown.md` why we are avoiding markdown links that
end in "))".

Ran `make www` to perform the above.

TODO: Fix stuff we broke by mistake doing the above.

TODO: Fix more broken markdown links.

faq.html

@@ -551,7 +551,7 @@ winners based on the same theme.</p>
 frequently submitted theme, be sure that it is obfuscated in several
 new and novel ways.</p>
 <p><strong>IMPORTANT HINT</strong>: Be sure to <strong>clearly explain</strong> near the beginning
-of your <code>remarks.md</code> file (see <a href="#remarks_md">FAQ 2.1</a>)
+of your <code>remarks.md</code> file, see <a href="#remarks_md">FAQ 2.1</a>,
 <strong>why you are submitting a entry based on a frequently
 submitted theme</strong> and <strong>how compares with previous IOCCC winners</strong>
 of the same theme.</p>
@@ -630,7 +630,7 @@ previous IOCCC entries make it more challenging to be successful.</p>
 state something along the lines of:</p>
 <pre><code>    We tend to dislike programs that: are similar to previous winning entries.</code></pre>
 <p><strong>FAIR WARNING</strong>: Be sure to <strong>clearly explain</strong> near the beginning
-of your <code>remarks.md</code> file (see <a href="#remarks_md">FAQ 2.1</a>)
+of your <code>remarks.md</code> file, see <a href="#remarks_md">FAQ 2.1</a>,
 <strong>why you are submitting a entry based on a frequently
 submitted theme</strong> and <strong>how compares with previous IOCCC winners</strong>
 of the same theme.</p>
@@ -851,7 +851,7 @@ entries</a>
 of the <a href="years.html#2020">IOCCC 2020</a>,
 after a far too long of a delay
 (due in part to a <a href="https://github.com/ioccc-src/winner/commit/c94fc84c35dc83e3eb9900720b95917a15c27afe">former IOCCC judge whose resignation was noted on
-2021 Jan 04</a>)
+2021 Jan 04</a> commit)
 from their initial <a href="https://web.archive.org/web/20200726232505/http://www.ioccc.org:80/index.html">2020 Jul 25
 announcement</a>,
 were added by an <a href="https://www.ioccc.org/judges.html">IOCCC judge</a>