The prefix "./" would be lost in mobile displays and when the browser viewport
is smaller than the container width.
This removes the left margin from the header for smaller displays. Also adds a scss variable
so that its easy to change the point where the "mobil" margin is applied.
The maximum width is currently set to 600px, while this works, it could
easily have an increased width (say 1000px), which would improve
readability of long code snippets.
