Improve keyboard navigation in calendar component

[sergei-maertens]

Package: @utrecht/component-library-react Component: Calendar

Currently you can only navigate inside the calendar using the Tab key which mostly works but is a bit awkward.

• Implement arrow key navigation: left, right and up/down to jump between weeks/days
• Tabbing to a date within the active month is okay, hitting enter selects the date -> ok
• Tabbing to a date in the previous/next month and hitting enter -> activates/navigates to that month, but not on the selected date (or the first/last of that month).

Resources:

https://blog.logrocket.com/how-to-build-an-accessible-date-picker-component-in-react/ seems particularly useful as they've implemented the keyboard navigation and it's also on top of date-fns