add topics

views/topics/edit.etlua

@@ -0,0 +1,12 @@
+<h1>Editing topic <%= topic.name %></h1>
+<form method="post">
+  <input type="text" name="name" id="name" value="<%= topic.name %>" placeholder="Topic name" required><br>
+  <textarea id="description" name="description" value="<%= topic.description %>" placeholder="Topic description"></textarea><br>
+  <input type="checkbox" id="is_locked" name="is_locked" value="<%= ntob(topic.is_locked) %>">
+  <label for="is_locked">Locked</label><br>
+  <input type="submit" value="Save changes">
+</form>
+<form method="get" action="<%= url_for("topic", {slug = topic.slug}) %>">
+  <input type="submit" value="Cancel">
+</form>
+<i>Note: to preserve history, you cannot change the topic URL.</i>