maintainers: add armeenm

maintainers/maintainer-list.nix

···
     githubId = 1118815;
     name = "Vikram Narayanan";
   };
+  armeenm = {
+    email = "[e-mail]";
+    github = "armeenm";
+    githubId = 29145250;
+    name = "Armeen Mahdian";
+  };
   armijnhemel = {
     email = "[e-mail]";
     github = "armijnhemel";