Give users the opportunity to close or dismiss a component with .btn-close. Although the default design is simple, it is very configurable. Change the Sass variables to a new background picture instead of the original one. As it is done with aria-label, make sure to add text for screen readers.
The opacity of disabled close buttons is altered. Pointer-events: none and user-select: none have also been used to stop hover and active states from triggering.