Add Bulgarian to Tails website weblate
The Bulgarian translators have translated the Tails GUI and want to translate Tails website, but it seems Bulgarian is not enabled on https://translate.tails.net/.
Could we add it? cc @zen
## To do
From [Enable a new language in Weblate](https://tails.net/contribute/working_together/roles/translation_platform/operations/#index1h1):
- [x] exclude the new language in the production website: [tails!1997](https://gitlab.tails.boum.org/tails/tails/-/merge_requests/1997)
- [x] add the new language to `$weblate_additional_languages`
- [x] add `.po` files to Git
- [x] update Weblate components
- [x] make sure the new `.po` files land in `tails.git`'s `master` branch
- [x] fix doc to add [the manual push to canonical](https://gitlab.torproject.org/tpo/tpa/tails-sysadmin/-/issues/18194#note_3170142)
- [ ] add reviewers
issue