[Tails-l10n] [announcement] pre-commit hook to validate PO f…

Hi,

FWIW there's now a script in ./bin/pre-commit-translation in our main
Git repository, that can be used as a pre-commit hook. It will do some
sanity checks on PO files.

For those of you who regularly modify PO files directly in Git (I
guess that's mostly some translators, tech writers and myself), it
might be useful to set it up as documented in the comments on top of
that file.

Note that the very same checks are run by our CI:

- Whenever we push to our master branch
- As part of the test suite we run after building Tails images

… so I feel no need for stronger encouragements nor for documenting
this in the various places where it might be useful (the vast majority
of the target audience for this pre-commit hook will not read such
documentation as they already have their development environment set
up).

Cheers,
--
intrigeri