The plugin's ftplugin doesn't work when opening vim.

When vimrc is
```vim
packadd nim.vim
filetype plugin on
```
and exec `vim test.nim` then shiftwidth is "2".

But when vimrc is
```vim
packadd vim-jetpack
call jetpack#begin()
Jetpack 'tani/vim-jetpack', {'opt': 1}
Jetpack 'zah/nim.vim'
call jetpack#end()
```
and exec `vim test.nim` then shiftwidth is "8". Exec `vim` and `:e test.nim`, shiftwidth is "2".

VIM 9.0
WSL2
Debian 12