Add Prometheus 3.13 as an LTS release

Signed-off-by: Julien Pivotto <291750+roidelapluie@users.noreply.github.com>

Author: roidelapluie

docs-config.ts

@@ -46,7 +46,7 @@ export default {
 
   // Long-term support versions configuration.
   ltsVersions: {
-    prometheus: ["3.5"],
+    prometheus: ["3.5", "3.13"],
   },
 
   // Repositories for the downloads page. The order in this file is the

docs/introduction/release-cycle.md

@@ -44,6 +44,9 @@ having a Prometheus server maintained by the community.
         <tr class="success">
             <td>Prometheus 3.5</td><td>2025-07-14</td><td>2026-07-31</td>
         </tr>
+        <tr class="success">
+            <td>Prometheus 3.13</td><td>2026-06</td><td>2027-07-31</td>
+        </tr>
     </tbody>
 </table>