set FAQ version

We add a FAQ version of "28.0 2024-07-14" to `faq.md`
using a similar form of version strings as `next/rules.md`
and `next/guidelines.md`.

Ran `make faq` to perform and test the above under macOS.

faq.html

@@ -383,6 +383,7 @@
 
 <!-- BEFORE: 1st line of markdown file: faq.md -->
 <h1 id="faq-table-of-contents">FAQ Table of Contents</h1>
+<p>This is FAQ version <strong>28.0 2024-07-14</strong>.</p>
 <h2 id="section-0---submitting-entries-to-a-new-ioccc">Section 0 - <a href="#faq0">Submitting entries to a new IOCCC</a></h2>
 <ul>
 <li><a class="normal" href="#faq0_0">0.0 - How may I enter the IOCCC?</a></li>