Check system-wide locations for hunspell

[OJFord]

Use of $LANGs other than en_US is broken for some Linux users (atom/spell-check#129).

Ideally, spellchecker should GetAvailableDictionaries from /usr/share/hunspell and whatever other common paths are in use (perhaps there is an environment variable similar to the XDG_*_HOMEs?) for dictionaries other than the single one shipped.

If that is the intention of GetAvailableDictionaries, it seems not to be working.

[P0oOOOo0YA]

@OJFord I'm still getting an empty array on Linux in almost 2019. So does it mean that this lib does not work on Linux?

[OJFord]

No idea in 2021; haven't tried using Atom for years.

I came here cleaning up some of my old stale issues; I think I'll leave this one open though, since some other people do seem to care about it (or at least did) and the lib seems.. lightly maintained still.