chore(web-forms#825): allow for forms app translation in transifex - #1692

Closes getodk/web-forms#825

Created as a draft so it's not merged until after release.

What has been done to verify that this works as intended?

Manual testing, and CI.

Why is this the best possible solution? Were any other approaches considered?

The other approach I attempted was to align with the process used in the web-forms package. It works using formatjs which is more lightweight than vue-intl. However it lacks the rich text feature because it doesn't precompile the locale, so couldn't handle HTML elements the app requires. I tried to add this functionality but it would have required either adding JIT compilation to central OR adding a compilation step to the package, either would add bloat just for a few messages in the forms app.

Ultimately because the forms and central app are being built with the same vite config it made more sense to align with the central approach (this PR).

How does this change impact users? Describe intentional behavior changes from code updates. What are the regression risks?

It shouldn't do. It means in future new and updated translations and locales can be added to transifex and updated in the forms app.

Does this change require updates to user documentation? If so, please file an issue here and include the link below.

No.