maintainers: add zahrun

maintainers/maintainer-list.nix

···
     githubId = 568532;
     name = "Christian Zagrodnick";
   };
+  zahrun = {
+    email = "[e-mail]";
+    github = "zahrun";
+    githubId = 10415894;
+    name = "Zahrun";
+  };
   zakame = {
     email = "[e-mail]";
     github = "zakame";