Manage jstoolbar translations with I18n

We have vendored jstoolbar translation as separate javascript files.

This PR aims to manage the jstoolbar translations with regular I18n to make them equal with all our other translations. This lets us add jstoolbar translations with crowdin \o/
That's the API of those formatting helpers. See: https://github.com/opf/openproject/blob/dev/lib/redmine/wiki_formatting/null_formatter/helper.rb#L37