maintainers: Add WhiteBlackGoose as a maintainer

maintainers/maintainer-list.nix

···
       fingerprint = "69C9 876B 5797 1B2E 11C5  7C39 80A1 F76F C9F9 54AE";
     }];
   };
+  WhiteBlackGoose = {
+    email = "[e-mail]";
+    github = "WhiteBlackGoose";
+    githubId = 31178401;
+    name = "WhiteBlackGoose";
+    keys = [{
+      fingerprint = "640B EDDE 9734 310A BFA3  B257 52ED AE6A 3995 AFAB";
+    }];
+  };
   wuyoli = {
     name = "wuyoli";
     email = "[e-mail]";