Add a \...End companion command to \AtEveryCite (and friends)

[dbitouze]

\AtEveryCite{⟨code⟩} lets us append the ⟨code⟩ to an internal hook executed at the beginning of every citation command.

That's nice but, sometimes, we need to append ⟨code⟩ at the end of every citation command so a \AtEveryCiteEnd companion command would be nice.

The feature request may apply to \AtEveryCite friends which let us append some ⟨code⟩ at the beginning of other tools.

[moewew]

See also #335. The exact placement of the ..EveryEnd vs ...NextEnd is not entirely trivial.

[aboruvka]

You could hook into the postnote or multipostnote fields. Otherwise there is no clear hook for "end", particularly for multi-citation commands.