add sorting topics view

views/mod/sort-topics.etlua

@@ -0,0 +1,19 @@
+<div class="darkbg settings-container">
+  <% if infobox then %>
+    <% render("views.common.infobox", infobox) %>
+  <% end %>
+  <h1>Change topics order</h1>
+  <p>Drag topic titles to reoder them. Press submit when done. The topics will appear to users in the order set here.</p>
+    <form method="post" id=topics-container>
+      <% for _, topic in ipairs(topics) do %>
+        <div draggable="true" class="draggable-topic" ondragover="dragOver(event)" ondragstart="dragStart(event)" ondragend="dragEnd()">
+          <div class="thread-title"><%= topic.name %></div>
+          <div><%= topic.description %></div>
+          <input type="hidden" name="<%= topic.id %>" value="<%= topic.sort_order %>" class="topic-input">
+        </div>
+      <% end %>
+      <input type=submit value="Save order">
+    </form>
+</div>
+
+<script src="/static/js/sort-topics.js"></script>

views/topics/topics.etlua

@@ -2,6 +2,7 @@
   <h1 class="thread-title">All topics</h1>
   <% if me:is_mod() then %>
     <a class="linkbutton" href="<%= url_for("topic_create") %>">Create new topic</a>
+    <a class="linkbutton" href="<%= url_for("sort_topics") %>">Sort topics</a>
   <% end %>
 </nav>