fix Support the IOCCC title on years.html

Fixed heading title for "Support the IOCCC" block in `years.html`.

Changed `bin/gen-years.sh` VERSION from  "2.1.0 2025-06-06"
to "2.1.1 2025-06-06".

Update sitemap.

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

years.html

@@ -435,8 +435,8 @@
 <table>
 <tr>
 <td colspan="3" style="padding-top: 12px;">
-<span class="pseudo_h3">  IOCCC on Social Media</span>
-<span class="small_click_below">   click below to visit</span>
+<span class="pseudo_h3">  Support the IOCCC</span>
+<span class="small_click_below">   click below to support</span>
 </td>
 </tr>
 <tr>