non standard keyboard navigation

[matoaaa]

According to standard:
https://raw.githack.com/w3c/aria-practices/issue57-date-picker-design-pattern/aria-practices.html#calendar-grid-keyboard-interaction

• Shift Page Up: Updates the calendar grid to the next year. instead of Alt+Page Up

• Shift Page Down: Updates the calendar grid to the previous month. instead of Alt+Page Down

• Home: Moves focus to first day of the current week. not to first day of current month

• End: Moves focus to the last day of the current week. not to last day of current month

[matoaaa]

partial fix in #59