maintainers: add samw

maintainers/maintainer-list.nix

···
     githubId = 107703;
     name = "Samuel Rivas";
   };
+  samw = {
+    email = "[e-mail]";
+    github = "wlcx";
+    githubId = 3065381;
+    name = "Sam Willcocks";
+  };
   samyak = {
     name = "Samyak Sarnayak";
     email = "[e-mail]";