fix: add margin to topic listing topics

src/tildes-baukula/_topic-listing.scss

@@ -1,6 +1,7 @@
 .topic-listing {
   // Make all the topics in the listing have the same background color
   > li:nth-of-type(n) {
+    margin-bottom: 0.2rem;
     background-color: $background;
   }
 }