Created by: ysds
Demo:
- Current: https://codepen.io/anon/pen/BxjyjL or the docs (3rd and 4th demo)
- After: https://codepen.io/anon/pen/mpobvb
.custom-file
will never be focused. The actual focusable element is .custom-file-input
and the correct target to apply z-index: 3
is .custom-file-label
.