The i18n-helpers are now available as a stand-alone crate:
https://crates.io/crates/mdbook-i18n-helpers.
Because we cache the Rust binaries in our GitHub workflows, I bumped
the cache prefix to ensure we use a clean cache. Otherwise, Cargo
won’t install the new binaries in mdbook-i18n-helpers because it sees
the old ones from this repository.
* Make i18n-helpers a requirement
* Skip mdbook-gettext for mdbook-xgettext
* Gettext finds PO file based on `book.language`
* Update workflow
No need to set `preprocessor.gettext.po-file`.
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Co-authored-by: Jooyung Han <jooyung@google.com>