Release v0.4.0

⚠️ Warning ⚠️

This plugin started using vim.api.nvim_create_augroup and vim.api.nvim_create_autocmd.
These are functions built-in since Neovim v0.7.0.
This version will work with Neovim 0.7.0 or lower but only with 0.7.0+ or higher in the next version.
(This plugin notifies WARNING to users affected by the next version or later.)