maintainers: add javimerino

maintainers/maintainer-list.nix

···
     githubId = 488556;
     name = "Javier Aguirre";
   };
+  javimerino = {
+    email = "[e-mail]";
+    name = "Javi Merino";
+    github = "JaviMerino";
+    githubId = 44926;
+  };
   jayesh-bhoot = {
     name = "Jayesh Bhoot";
     email = "[e-mail]";