Provide an option to dismiss or close a component with .btn-close.
Default styling is limited, but highly customizable. Modify the Sass
variables to replace the default background-image. Be sure to include
text for screen readers, as we’ve done with aria-label.
Disabled state
Disabled close buttons change their opacity. We’ve also applied
pointer-events: none and user-select: none to preventing hover and
active states from triggering.