Add Indonesian translation of Mailing List FAQ article

As this is a new language in the FreeBSD documentation, other
files/translations were added together.

Reviewed by: dbaio (translating it back to English)
Approved by: dbaio (doceng)

Differential Revision: https://reviews.freebsd.org/D34599
Co-authored-by: Danilo G. Baio <dbaio@FreeBSD.org>