Add freshrss

As services.freshss wasn't working and not logging in, I've used Docker
for this.

nix/modules/nixos/features/homelab/freshrss/default.nix

@@ -0,0 +1,19 @@
+{ pkgs, lib, ... }:
+
+let
+  port = 4003;
+in
+{
+  imports = [ ./container.nix ];
+
+  services.nginx = {
+    enable = true;
+
+    virtualHosts."freshrss.davies.home".locations."/".proxyPass = "http://localhost:${toString port}/";
+  };
+
+  # TODO: move to pihole.
+  networking.hosts = {
+    "127.0.0.1" = [ "freshrss.davies.home" ];
+  };
+}