Support translation

[drimpact]

• On build gather translations from crowdin
• For languages with decent coverage, include them as a language option in the header/footer
• Translated pages should exist on a language specific path as per SEO guidelines
• Only pages with good coverage in a language should be included in the sitemap.xml
• Translated pages should have a meta link back to the original content for SEO
• The language shown should be based on the browser's language

[drimpact]

Localisation Support

[drimpact]

Rough plan:

• Use gatsby's react-i18next plugin
• Use keys for translations, rather than english strings which were used in the app. Allows some adjustments without forcing people to re-translate. Keys should be separated by page so page coverage can be assessed.
• Generate localised pages (/lang/ prefix) for every language with some translations available
• Only include languages with good coverage in the footer/header
• For pages with poor translation coverage, include a meta robot noindex header. Will need to run a script on build to assess which pages are not suitable and feed through to helmet. These pages can remain in headers, as the noindex header will stop google from indexing (see duplicate content guidance)
• No need to include translated pages in sitemap, just rely on the i18n headers. See guidance
• Don't automatically redirect users, provide language flags and rely on google to send people to the right place, See google guidance
• No need to use ICU strings this time as there isn't dynamic messaging. Could use to remain consistent tho...