maintainers: update natsukagami

With email matching GPG key, and other info

maintainers/maintainer-list.nix

···
     name = "Nathan Yong";
   };
   natsukagami = {
-    email = "[e-mail]";
+    name = "Natsu Kagami";
+    email = "[e-mail]";
+    matrix = "@nki:m.nkagami.me";
     github = "natsukagami";
     githubId = 9061737;
-    name = "Natsu Kagami";
     keys = [ { fingerprint = "5581 26DC 886F E14D 501D  B0F2 D6AD 7B57 A992 460C"; } ];
   };
   natsukium = {