`spellfile` is set to an arbitary value and does not respect the first word-list declaration in `spelllang`

[alesandar]

First of all, thanks a lot for that lovely neovim configuration boilerplate!

I have found that there's a typographical error in your spellfile option.

dope/lua/core/options.lua

Line 15 in d2ba3a6

opt.spellfile = cache_dir .. 'spell/en.uft-8.add'

spell/en.uft-8.add should be spell/en.utf-8.add.

Furthermore, if spelllang was set to something different (e.g. bg) upon startup - the default fallback of spellfile will be changed to bg.utf-8.add. Note that it seems like neovim won't update the value of spellfile dynamically, unless it was initially set.

I have also found that using multiple spelllangs will make force neovim to fallback to the one that has been declared first.

For example:
:se spelllang=en,bg will fallback to en.utf-8.add,
:se spelllang=bg,en will fallback to bg.utf-8.add,

I was able to mimic neovim's default spellfile behaviour (while preserving the cache_dir path) by doing so:
opt.spellfile = cache_dir .. opt.spelllang:get()[1] .. '.utf-8.add'

Let me know if that makes sense to you and I will make a PR.

[glepnir]

maybe we can simply removed this. if someone want a spell just add it on his local right ?