[nvim] Only spellcheck in text files

nvim-init.vim

@@ -163,10 +163,13 @@ nnoremap <silent> <leader>ml :call AppendModeline()<CR>
 
 " Spell check {{{2
 " ================
-set spell
-set spelllang=en_us,nl
+set spelllang=en_uk,nl
 set spellfile=$HOME/.local/share/nvim/spellfile.utf-8.add
 
+augroup spellcheck_textfiles
+  au! BufNewFile,BufRead *.md,*.txt,*.tex setlocal spell
+augroup END
+
 
 " Plug-ins {{{1
 " =============