Add simple route-based code splitting

src/App.scss

@@ -1,10 +1,18 @@
 @import "sass/config";
 
+.main {
+  min-height: 85vh;
+}
+
+html, body {
+  padding: 0;
+  height: 0;
+}
+
 body {
   color: white;
   background-color: #111;
   font-family: Verdana;
-  margin: 0;
 }
 
 // Normalize etc.
@@ -52,10 +60,6 @@ a {
   }
 }
 
-.index {
-  min-height: 85vh;
-}
-
 .index__class-picker {
   margin: 2em 0;
 }