I tested your new patches and it worked perfectly for me. When can we
merge it so I can remove the hack I added in my configuration? 😄

ps:

We can add `elixir-ts-mode` to `auto-mode-alist` by:

```elisp
(add-to-list 'auto-mode-alist
             '("\\(\\.elixir\\|\\.exs?\\|mix\\.lock\\)\\'"
               . elixir-ts-mode))
```

It might be redundant to write `add-to-list` 4 times, and other
major-modes are added to `auto-mode-alist` by writing `add-to-list`
just once.