fix: ensure langDir is escaped on Windows

[kedrzu]

After updating nuxt-i18n my project stopped compiling.
After some digging, I've found this problem:

I'm working on windows, and paths do use backslashes.
When creating script templates this requires for string to be properly escaped.

It's enough to pass it through JSON.stringify, so I think easiest way to fix that, was to remove the special case for string.
Also, checking for boolean and null should also be unnecessary - JSON.stringify should handle it as well.

PS: this would also break if there were ' characters anywhere inside.

[rchl]

I think the issue is deeper than that. Do the ASYNC_LOCALES variables look OK in the options.js?

I think it will look something like this which doesn't seem correct:

[rchl]

Or maybe that's just on my system because I'm forcing a Windows path on MacOS?

[kedrzu]

It didn't look so bad. Slashes were mixed (backslashes and standard ones), but they are at least escaped properly.

[rchl]

Thanks!
Released in v6.20.6