Collect Gitea metrics in Prometheus

Reviewed-by: Aleix Roca Nonell <aleix.rocanonell@bsc.es>

m/hut/monitoring.nix

@@ -160,6 +160,10 @@
           }
         ];
       }
+      {
+        job_name = "gitea";
+        static_configs = [{ targets = [ "127.0.0.1:3000" ]; }];
+      }
       {
         # Scrape the IPMI info of the hosts remotely via LAN
         job_name = "ipmi-lan";