Per T108422, we would like to add basic i18n support to the Copyvio Detector tool on Tool Labs (https://tools.wmflabs.org/copyvios/).
Acceptance criteria:
- You can set UI language via query string, e.g. ?uselang=es (so that links from particular projects can pre-set the language)
- uselang query string parameter is preserved while navigating to tool settings page and back
- Language can be set explicitly from the settings page and stored in a cookie
- Language cookie can be deleted via the settings page (same as other Copyvio Detector cookies)
- i18n architecture must be easily extendable for adding new languages (this probably means that you want to create separate i18n files for each language and have some sort of key for each i18n string that gets mapped to a translated string in the i18n files)
- Should support at least 1 language besides English (pick a language you know or can easily get translations for)