format headers

We move `tmp/format-headers.sh` into `bin/format-headers.sh`.

We also add a few missing empty lines to `README.md`.

We add `bin/format-headers.sh` to the `bin/README.md`.

We run `bin/format-headers.sh` to perform the above.

Performed `make www` to accomplish the above and to test under macOS.

2020/otterness/README.md

@@ -53,7 +53,7 @@ with the MIDI "SMF" file format.
 entry](https://www.nathanotterness.com/2021/04/obfuscated_c_2020.html).
 
 
-## Alternate use:
+### Alternate use:
 
 Use `prog.alt` as you would `prog`.
 

2020/otterness/index.html

@@ -437,7 +437,7 @@ with the MIDI “SMF” file format.</p>
 </blockquote>
 <p>… at their <a href="https://www.nathanotterness.com/2021/04/obfuscated_c_2020.html">web page about the
 entry</a>.</p>
-<h2 id="alternate-use">Alternate use:</h2>
+<h3 id="alternate-use">Alternate use:</h3>
 <p>Use <code>prog.alt</code> as you would <code>prog</code>.</p>
 <h3 id="alternate-try">Alternate try:</h3>
 <pre><code>     ./try.alt.sh</code></pre>