mininet: init at 2.3.0d4 (#41261)

Mininet (https://github.com/mininet/mininet) is a popular network emulator that
glues several components such as network namespaces, traffic control
commands into a set of python bindings. It is then "easy" to describe a
topology and run experiments on it.

nixos/modules/module-list.nix

@@ -103,6 +103,7 @@
   ./programs/less.nix
   ./programs/light.nix
   ./programs/mosh.nix
+  ./programs/mininet.nix
   ./programs/mtr.nix
   ./programs/nano.nix
   ./programs/npm.nix