Enable chronological sorting by birth date

[alulsh]

Currently, the birth date column in the family tree table sorts alphabetically and not chronologically. For example, August 29, 1959 sorts before August 6, 1892.

According to the datatables documentation, we can enable chronological sorting through a data-order or data-sort attribute in the birth date td element.

We can set the data-order value to the Unix timestamp using dayjs().unix() for easy sorting.