Autogenerate .spl files from .add spelling files

.vimrc

@@ -271,6 +271,15 @@ endif
 " https://castel.dev/post/lecture-notes-1/
 inoremap <C-l> <c-g>u<Esc>[s1z=`]a<c-g>u
 
+" Make sure .add.spl spelling files are up-to-date with their .add
+" counterparts
+" https://vi.stackexchange.com/questions/5050/how-to-share-vim-spellchecking-additions-between-multiple-machines
+for d in glob('~/.vim/spell/*.add', 1, 1)
+    if filereadable(d) && (!filereadable(d . '.spl') || getftime(d) > getftime(d . '.spl'))
+        exec 'mkspell! ' . fnameescape(d)
+    endif
+endfor
+
 " Word completion from dictionary (on ctrl+space)
 set complete+=kspell