PWABuilder shows language warnings when using language codes like "EN-gb" or "DE-de"

@Grevil: Maybe it's just the upper / lower case, which seems wrong:

For example, the 'en-AU' language range represents English as spoken in Australia, and 'fr-CA' represents French as spoken in Canada

So it should be en-GB not EN-gb

Wow.. thanks!

Just a fix description change, no need for review.

Automatically closed - issue fixed for 2 weeks with no activity.