improve use of Support the IOCCC, Social Media code blocks

Changed "Support IOCCC" heading to "Support the IOCCC".

Use HTML blockquote instead of markdown quote for the "Support the IOCCC"
and "IOCCC on Social Media" HTML code blocks.

Added "Support the IOCCC" and "IOCCC on Social Media" to the
top level `index.html` page, the top level `news.html` page and
the top level `years.html` page.

Changed `bin/gen-years.sh` VERSION from "2.0.0 2025-03-13"
to "2.1.0 2025-06-06".

Update sitemap.

Tested the above via `make gen_top_html gen_years timestamp` on macOS.

sitemap.xml

@@ -15278,7 +15278,7 @@
 </url>
 <url>
     <loc>https://www.ioccc.org/bin/gen-years.sh</loc>
-    <lastmod>2025-04-16T20:59:19+00:00</lastmod>
+    <lastmod>2025-06-07T02:00:47+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/bin/html.sed</loc>
@@ -15450,11 +15450,11 @@
 </url>
 <url>
     <loc>https://www.ioccc.org/index.html</loc>
-    <lastmod>2025-06-07T01:09:58+00:00</lastmod>
+    <lastmod>2025-06-07T02:01:44+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/index.md</loc>
-    <lastmod>2025-06-07T01:11:42+00:00</lastmod>
+    <lastmod>2025-06-07T02:01:35+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/ioccc.css</loc>
@@ -15498,11 +15498,11 @@
 </url>
 <url>
     <loc>https://www.ioccc.org/news.html</loc>
-    <lastmod>2025-06-07T01:20:38+00:00</lastmod>
+    <lastmod>2025-06-07T02:01:46+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/news.md</loc>
-    <lastmod>2025-06-07T01:20:13+00:00</lastmod>
+    <lastmod>2025-06-07T02:01:18+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/next/guidelines.html</loc>
@@ -15598,11 +15598,11 @@
 </url>
 <url>
     <loc>https://www.ioccc.org/status.html</loc>
-    <lastmod>2025-06-07T01:20:45+00:00</lastmod>
+    <lastmod>2025-06-07T02:03:20+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/status.json</loc>
-    <lastmod>2025-06-07T01:20:44+00:00</lastmod>
+    <lastmod>2025-06-07T02:03:19+00:00</lastmod>
 </url>
 <url>
     <loc>https://www.ioccc.org/status.md</loc>
@@ -15626,6 +15626,6 @@
 </url>
 <url>
     <loc>https://www.ioccc.org/years.html</loc>
-    <lastmod>2025-01-26T20:59:52+00:00</lastmod>
+    <lastmod>2025-06-07T02:03:18+00:00</lastmod>
 </url>
 </urlset>