add layout file and add helper

layouts/verenigingen.erb

@@ -1,5 +1,10 @@
 <ul>
-<% @items.find_all("**/verenigingen/*").sort_by {|x| x[:naam]}.each do |i| %>
-    <li> <%= link_to(i[:naam], i) %> </li>
-<% end %>
-<ul>
+    <% for vereniging in themes %>
+        <li> <%= vereniging %> </li>
+    <% end %>
+</ul>
+<ul>
+    <% for konvent in konvents %>
+        <li> <%= konvent %> </li>
+    <% end %>
+</ul>

lib/helpers/verenigingen.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+# Helpers for navbar partial
+module VerenigingenLists
+    def current_child_of(item)
+        child_of(item, @item)
+    end
+  
+    def child_of(parent, child)
+        children_of(parent).include?(child)
+    end
+  
+    # Returns every navigable item
+    # A navigable item contains the :navigable attribute
+    # Optionally contains an order attribute, determining the order in the navbar
+    def themes
+        @items.find_all("**/verenigingen/*").map{|x| x[:themas]}.flatten.uniq.compact
+    end
+    def konvents
+        @items.find_all("**/verenigingen/*").map{|x| x[:konvent]}.uniq.compact
+    end
+  end

lib/helpers_.rb

@@ -2,4 +2,5 @@ use_helper Nanoc::Helpers::LinkTo
 use_helper Nanoc::Helpers::Rendering
 use_helper Nanoc::Helpers::ChildParent
 
-use_helper NavigationHelper
+use_helper NavigationHelper
+use_helper VerenigingenLists