maintainers: add theonlymrcat

maintainers/maintainer-list.nix

···
     githubId = 71843723;
     keys = [ { fingerprint = "EEFB CC3A C529 CFD1 943D  A75C BDD5 7BE9 9D55 5965"; } ];
   };
+  theonlymrcat = {
+    name = "Max Guppy";
+    email = "[e-mail]";
+    github = "TheOnlyMrCat";
+    githubId = 23222857;
+  };
   theoparis = {
     email = "[e-mail]";
     github = "theoparis";