This site is hosted on the GitBook platform, which lets users update the documentation, like in a Wiki. Making changes is super easy because it's done directly in the internet browser, nothing to install.
You can also help by fixing or adding new translations. Currently there is 2 languages, English and Japanese. If you language does not exist yet, contact me (here) so that I add a "GitBook variant" for that language.
H. Sakuda. : who created the Japanese doc pages