Make .highlight smaller to avoid splitting text (#1136)

The headlines on the website are unnecessarily difficult to read due to the text being split in half by two different backgrounds with a hard border. This makes the highlight a little smaller and a little lower so it looks more like a thick underline.

Author: mjbshaw

src/styles/app.scss

@@ -342,9 +342,9 @@ h3 {
 }
 
 .highlight {
-  height: 24px;
+  height: 12px;
   position: relative;
-  top: -24px;
+  top: -6px;
   left: -10px;
   width: 120%;
   max-width: 90vw;