Allow locale and language being set via URL param

[tordans]

With the hash-url locale=en-US or locale=de-DE one can force a locale and language regardless of the given language from the osm-website-settings.

This is to solve #5644.

However, while looking into this I understood that the interface language is in fact pulled from the OSM-website-profile-language (not the browser language). So there is a way to change the language, by editing the preferred languages in the profile.

So while this PR makes changing the language a bit easier and quicker, I am not sure if it is worth the added complexity.

In case this should be continued, those thinks are todo IMO:

• This line https://github.com/openstreetmap/iD/blob/master/modules/util/detect.js#L93 is duplicated now, should it be removed?
• Should there be specs for this? If so, I don't know enough about specs to write good ones.

[bhousel]

[ ] This line https://github.com/openstreetmap/iD/blob/master/modules/util/detect.js#L93 is duplicated now, should it be removed?

Yes, it's unnecessary to do it twice. You could put the line once at the top of the function if the q hash will be used in a few places.

Should there be specs for this? If so, I don't know enough about specs to write good ones.

I'm not sure we can test this feature, because I'm guessing window.location.hash from within the tests would cause issues. This is ok.

[tordans]

@bhousel ready for review. Thanks.

[bhousel]

Thanks @tordans - looks good!
Could you also add a short description of the parameter here: https://github.com/openstreetmap/iD/blob/master/API.md