Revert "remove unneccesary position: fixed"

This reverts commit a4c2f562cf60cbe3f3545d2893b1438596f20c44.

Turns out it was necessary!

h/sass/app.scss

@@ -11,6 +11,7 @@ body {
   background-color: transparent;
   font-family: $sansFontFamily;
   height: 100%;
+  position: fixed;
   width: 100%;
 }