maintainers: add kittywitch

maintainers/maintainer-list.nix

···
     githubId = 148352;
     name = "Jim Fowler";
   };
+  kittywitch = {
+    email = "[e-mail]";
+    github = "kittywitch";
+    githubId = 67870215;
+    name = "kat witch";
+    keys = [{
+      longkeyid = "rsa4096/0x7248991EFA8EFBEE";
+      fingerprint = "01F5 0A29 D4AA 9117 5A11  BDB1 7248 991E FA8E FBEE";
+     }];
+  };
   kiwi = {
     email = "[e-mail]";
     github = "Kiwi";