Modal: Implement focus trap

This PR proposes a solution to trap focus within a modal. This improves keyboard navigation and overall accessibility. According to [Focus Order (Level A)](https://www.w3.org/WAI/WCAG22/Understanding/focus-order.html) from [WCAG 2.2](https://www.w3.org/WAI/WCAG22/Understanding/) - _A web page implements modal dialogs via scripting. When the trigger button is activated, a dialog opens and focus is set within the dialog. As long as the dialog is open, focus is limited to the elements of the dialog. When the dialog is dismissed, focus returns to the button or the element following the button._ I previously submitted a similar [PR](https://github.com/themesberg/flowbite-vue/pull/367) to [Flowbite Vue](https://github.com/themesberg/flowbite-vue).