[nvim] Add spellchecking shortcuts to vim

<leader>O to enable spellchecking for current buffer,
<leader>o to show suggestiong for word under curser.

(Try it out here, just hover over misspelled cursor!)

.config/nvim/init.vim

@@ -380,6 +380,10 @@ nnoremap <leader>\ :vsp<cr>
 nnoremap <tab> %
 nnoremap <tab> %
 
+" Spell-check set to <leader>O, 'o' for 'orthography':
+noremap <leader>O :setlocal spell! spelllang=en_us<CR>
+noremap <leader>o z=
+
 " select the whole buffer with <leader>-a
 nnoremap <leader>a ggVG