fix: focus lost when navigation button is disabled

[gpbl]

Fixes issue #2630 by replacing the disabled attribute with aria-disabled, to prevent the focus loss when navigating to the last month.

After some research, I believe this change won’t cause any other accessibility issues.

Breaking change (style): This change may affect the style of those who rely on the [disabled]/:disabled CSS selectors. To fix this, use aria-disabled instead.

- .rdp-button_next[disabled="true"],
- .rdp-button_next:disabled,
+ .rdp-button_next[aria-disabled="true"],
- .rdp-button_previous:disabled,
- .rdp-button_previous[disabled="true"],
+ .rdp-button_previous[aria-disabled="true"] {
   /* Existing custom style */
}

2025-02-16.18.30.02.mov