feat: i18n locale auto-detect (issue #153)

[tomers]

This PR makes the app auto-detect browser locale and set it.

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

The local selection behavior would change. It will now select the locale from the browser, instead of from the hard-coded default.

[IlCallo]

There are a couple of problems here:

• navigator.userLanguage isn't standard and should be removed, since we don't support IE anymore
• the PR should be rebased on latest changes for Qv2 (both on Quasar and vue-i18n side)
• why is String(...) used? Doesn't navigator.language always return a string?
• there's no default language in case the one from the browser isn't available into messages object. fallbackLocale option will help in those cases, but it will emit a lot of warnings

Can you address these problems?

[MatthewSH]

I just happened to notice this and figured I'd also respond.

To respond directly to you @IlCallo, yeah. It does return a DOMString/String. Not sure why we're creating a string again, maybe a precaution for that off chance you get a weird locale back that's not valid, but then it would use fallbackLocale in that case.

The code should probably be:

locale: navigator.language || 'en-us'

However, here's something else. If we wanted to support auto-detection of the locale through navigator, couldn't we opt for possibly something like this?

locale: navigator.languages[0] || navigator.language || 'en-us'

Languages will return an array of preferred languages if I can recall correctly and the navigator.language comes from that. I don't know, may not be worth the extra effort because, although it's widely supported in current browser versions, it [navigator.languages] may still be marked as experimental.