maintainers: add jaduff

maintainers/maintainer-list.nix

···
     githubId = 7558482;
     name = "Jack Gerrits";
   };
+  jaduff = {
+    email = "[e-mail]";
+    github = "jaduff";
+    githubId = 10690970;
+    name = "James Duff";
+  };
   jagajaga = {
     email = "[e-mail]";
     github = "jagajaga";