[NTG-context] modify kern between two glyphs

[mf]

Hello list,

I need to modify the kern between two glyphs.

This is a MWE where the problem is solved manually:

------------------------------------------
\mainlanguage[it]
\starttext

Default: «Questo è successo nel ’48».

Desired: «Questo è successo nel ’\kern-.1em 48».

\stoptext
------------------------------------------

Is it possible to solve it globally and only for a single font?

Thanks,
Massi