The new version is looking good, I did not find a way to add date rangers, I did some testing and this is what I found:
Input fields, select fields etc this is for the default plugin styles or functionalities…:
Focus Identifier should have a contrast ratio of at least 3:1
https://www.w3.org/WAI/WCAG21/Understanding/contrast-minimum
The focus identifier should display as a solid outline around the actionable field and fully visible ( The default styles is hard to notice so recommended ) Understanding Success Criterion 2.4.13: Focus Appearance | WAI | W3C
Date Picker:
Focus identifier as above and is even harder to notice.
Ensure that all content can be accessed with the keyboard alone. this part fails when using the date picker, users can only navigate through the days to get to a month they need to press the arrows to the first day or last day of the month, there is no way with keyboard to access the month and year drop down on the top of the datepicker.
https://www.w3.org/WAI/WCAG22/Understanding/keyboard-accessible
Imagine the scenario a keyboard users is on the calendar widget and wants to search 15 years ago, or 8 months back, the way it is working right now would not be efficient, and hard to reach, even if they can type the year or dat, since there is a calendar widget it needs all its elements to be able to be accessed by keyboard.
On the same Calendar widget the focus order after using the arrow keys to select a day, if I press the tab key, it jumps to the first element on the page (Skip Content link for example), this focus sequence is wrong and fails for https://www.w3.org/WAI/WCAG22/Understanding/focus-order
Another issue with the datepicker, after picking a date if using the keyboard i remove the date the focus on the field is not visible.
Hope this helps to improve the plugin, it is looking great hope to be able to use the final version soon.