[Tails-l10n] Automated check of PO files on the master branc…

Hi,

whenever something is pushed to the master branch, a Jenkins job is
checking that PO files in there are well-formed (using our good ol'
check_po.sh script, that was improved to be suitable for this task).

>From now on, if there are failures, or if it's back to "normal", then
this list will get a notification email.

It's the first time that we deploy such a thing, so I'm curious what
kind of contributor experience it creates => if you have comments or
complains about it in the future, please tell
tails-sysadmins@??? :)

Cheers,
--
intrigeri