Restore sortable option in official sphinx_theme

A table sorting option had been introduced specifically in Bio-Formats to sort the formats table.
This PR restores this option as part of the common sphinx theme.

To test this PR:
- check the formats tables in the staging documentations (bio-formats4, bio-formats5) are sortable
- check no other table is affected by this change in the other documentations

/cc @hflynn, @ctrueden