[feature request] Automatic tracking of translation progress

[edimitchel]

As ryu-cho is making github sync of translated docs, we could easily dedicate an issue which could be updated by ryu-cho and raise a tree of translation completion on each md files + updating the title to give the percentage of translations, where a page translated more than 80% is considered as fully translated.

The diff could be made by comparing the current version with the version of the file using the track-from sha1.