maintainers: add ImUrX

maintainers/maintainer-list.nix

···
     githubId = 4085046;
     name = "Imuli";
   };
+  imurx = {
+    email = "[e-mail]";
+    github = "imurx";
+    githubId = 3698237;
+    name = "ImUrX";
+  };
   inclyc = {
     email = "[e-mail]";
     github = "inclyc";