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/
I'm pretty much opposed to adding any inline JavaScript as I hope we'll one day be able to disable inline scripts via content security policy.

Couldn't we use i18n-js for this? (Assuming that's still our up-to-date method of giving translations to JavaScript. If not, we're probably already using another method for Angular.)