maintainers: create sage team

Maintaining all the packages whose updates might break some aspect of
sage.

For reference:
https://github.com/NixOS/nixpkgs/pull/103810#issuecomment-727536510

pkgs/development/libraries/science/math/libhomfly/default.nix

@@ -29,7 +29,7 @@ stdenv.mkDerivation rec {
     homepage = "https://github.com/miguelmarco/libhomfly/";
     description = "Library to compute the homfly polynomial of knots and links";
     license = licenses.unlicense;
-    maintainers = with maintainers; [ timokau ];
+    maintainers = teams.sage.members;
     platforms = platforms.all;
   };
 }