nix: enable buildbot badges

Just enough config to make this easily extensible in the future.

nix/master.nix

@@ -5,6 +5,14 @@
 }:
 let
   cfg = config.services.buildbot-nix.master;
+
+  # The start of a mergeable settings infrastructure.
+  www_config = {
+    plugins = {
+      # https://docs.buildbot.net/current/manual/configuration/www.html#badges
+      badges = { };
+    };
+  };
 in
 {
   options = {
@@ -145,6 +153,7 @@ in
       extraImports = ''
         from datetime import timedelta
         from buildbot_nix import GithubConfig, NixConfigurator, CachixConfig
+        import json
       '';
       configurators = [
         ''
@@ -183,9 +192,19 @@ in
         ps.treq
         ps.psycopg2
         (ps.toPythonModule pkgs.buildbot-worker)
+        pkgs.buildbot-plugins.badges
         pkgs.buildbot-plugins.www-react
         (pkgs.python3.pkgs.callPackage ../default.nix { })
       ];
+
+      extraConfig = ''
+        # WOOT
+        c['www'] = json.loads(
+          ''''
+          ${builtins.toJSON www_config}
+          ''''
+        )
+      '';
     };
 
     systemd.services.buildbot-master = {