Get language is broken when locale part of language code is lowercase

[radeno]

By this commit #169

there is bug when accept language is set in whole lowercase characters. For example in Safari browser is accept language sent as
Accept-Language: en-us
in chrome:
accept-language: en-US,en;q=0.9,sk;q=0.8

Lannguage code instead en is returned as en-

So regex /(([a-z]{2})-?([A-Z]{2})?)\s*;?\s*(q=([0-9.]+))?/g fails when is language passed as en-us because it excepts uppercase characters.

Example here: https://regex101.com/r/2mmR4w/2

Regex should be defined with insensitive flag i:

/(([a-z]{2})-?([A-Z]{2})?)\s*;?\s*(q=([0-9.]+))?/gi

[jamuhl]

Feel free to provide a PR if like to see this landed soon - else i will add it next time i work on this project.