document the mailinblack plugin

Hello,

we have a new plugin mailinblack and it should be documented only in 1.4-dev

Cheers

changed due date to June 15, 2021

marked this issue as related to fd-plugins#6115 (closed)

assigned to @cchilliet and unassigned @bmortier

changed milestone to %FusionDirectory 1.4

added PJ2105-0419 label

added plugin-mailinblack label

changed the description

mentioned in commit 464f504c

mentioned in commit 0494f6e8

mentioned in commit b9caa2fe

added 1h of time spent

removed due date

added Added label