improve rules & guidelines

Added a number of change bars to the rules & guidelines.

Recommend recommend that all markdown files in your submission observe
[IOCCC markdown guidelines](../markdown.html).

Made use of "_..._" consistent in the rules & guidelines.

Updated some the fun guidelines.

Performed some whitespace cleanup in the rules & guidelines.

Changed IOCCC Rules to version **29.12 2025-12-01**.
Changed IOCCC Guidelines to version **29.04 2025-12-01**

Ran `make quick_www` to perform the above.

sitemap.xml

@@ -16826,11 +16826,11 @@
 </url>
 <url>
     <loc>https://www.ioccc.org/next/guidelines.html</loc>
-    <lastmod>2025-12-01T09:13:14+00:00</lastmod>
+    <lastmod>2025-12-01T10:26:00+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/next/guidelines.md</loc>
-    <lastmod>2025-12-01T09:13:08+00:00</lastmod>
+    <lastmod>2025-12-01T10:20:36+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/next/index.html</loc>
@@ -16870,11 +16870,11 @@
 </url>
 <url>
     <loc>https://www.ioccc.org/next/rules.html</loc>
-    <lastmod>2025-12-01T09:04:25+00:00</lastmod>
+    <lastmod>2025-12-01T10:26:00+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/next/rules.md</loc>
-    <lastmod>2025-12-01T09:06:35+00:00</lastmod>
+    <lastmod>2025-12-01T10:21:01+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/next/submit.html</loc>