maintainers: add cmm to maintainers

maintainers/maintainer-list.nix

···
     githubId = 20808761;
     name = "cmfwyp";
   };
+  cmm = {
+    email = "[e-mail]";
+    github = "cmm";
+    githubId = 718298;
+    name = "Michael Livshin";
+  };
   cobbal = {
     email = "[e-mail]";
     github = "cobbal";