maintainers: add nils-degroot

maintainers/maintainer-list.nix

···
     githubId = 26231126;
     name = "Nils ANDRÉ-CHANG";
   };
+  nils-degroot = {
+    email = "[e-mail]";
+    github = "nils-degroot";
+    githubId = 53556985;
+    name = "Nils de Groot";
+  };
   ninjatrappeur = {
     email = "[e-mail]";
     github = "ninjatrappeur";