How/where should we document ?locale= and ?lang= params

[buren]

#450 adds support for locale= and lang= parameters, however they aren't that discoverable ;)

[bex1]

Yeah. Looking through the source and one may stumble upon them isn't an ideal scenario hehe. Maybe each page can have some documentation or each route in ja-routes if we want to keep it close to the code.

Or we add some seperate document for it.

[buren]

I'd like to have this kind of functionality discoverable(-ish) by non-devs, perhaps we could add some markdown file to a docs/ folder or somehing like that? Where we can keep track of these sort of things.