How to automatically update neovim's spell checker

add to lua/config/autocmds.lua:

-- Spell files auto-compilation
local function compile_spell_file(filepath)
  -- Only process .add files
  if not filepath:match("%.add$") then
    return
  end

  -- Compile the spell file
  vim.cmd("mkspell! " .. vim.fn.fnameescape(filepath))
  vim.notify("Compiled spell file: " .. filepath, vim.log.levels.INFO)
end

-- Auto-compile spell files when written
vim.api.nvim_create_autocmd({ "BufWritePost" }, {
  pattern = { "*.add" },
  callback = function(ev)
    compile_spell_file(ev.file)
  end,
  desc = "Auto-compile spell files on save",
})

-- Auto-compile spell files when externally modified
vim.api.nvim_create_autocmd({ "FileChangedShellPost" }, {
  pattern = { "*.add" },
  callback = function(ev)
    compile_spell_file(ev.file)
  end,
  desc = "Auto-compile spell files on external modification",
})

-- Check for missing .spl files on startup
vim.api.nvim_create_autocmd({ "VimEnter" }, {
  callback = function()
    local spell_dir = vim.fn.stdpath("config") .. "/spell"
    if vim.fn.isdirectory(spell_dir) == 1 then
      local add_files = vim.fn.glob(spell_dir .. "/*.add", false, true)
      for _, add_file in ipairs(add_files) do
        local spl_file = add_file:gsub("%.add$", ".spl")
        if vim.fn.filereadable(spl_file) == 0 then
          compile_spell_file(add_file)
        end
      end
    end
  end,
  desc = "Generate missing .spl files for existing .add files",
})