Building a better way to write posts in multiple languages

What this post added

Introduced a new multilingual composer for Pages and began testing for individual users, allowing a single post to be written in multiple languages. This involved developing new composer components using React and Flux, a storage implementation using 'author translations' (separate TAO objects for each language) instead of concatenation, and a server-side viewing experience that determines the most relevant language version for each viewer based on language preferences, locale, and common posting language. Machine translation is used to pre-fill additional language versions.