.btn backgrounds
Created by: MartijnCuppens
a.btn
doesn't have a background, button.btn
has a background (browser default)
See https://codepen.io/MartijnCuppens/pen/pZpxmr
If we add background-color: transparent;
to .btn
the 2 elements are rendered the same. We can than also remove this line from the .btn-outline-*
buttons.