Add a bit of left padding back to topics on mobile

This was too close to the left edge, especially when there was a
"highlight stripe" present, like on your own topics.

tildes/scss/modules/_topic.scss

@@ -31,6 +31,7 @@
 
   position: relative;
 
+  padding-left: 0.2rem;
   @media (min-width: $size-sm) {
     padding: 0.4rem;
   }