doesn't warn when dir is missing

[teto]

I had to install my config on a new setup and had some trouble because rocks-git was missing, because of this line:

[plugins."rocks-git.nvim"]

dir = "/home/teto/rocks-git.nvim"

The folder didn't exist on the new computer. I wonder how to address this. Should it be an error ? I am fine with this being optional but it should at least display a warning in :Rocks log. On top of that it could be a checkhealth ?

I am ready to do the work

[mrcjkb]

We probably want to display a similar warning to the one rocks.nvim displays when one or more plugins are not installed:

warning[rocks-dev]: The following plugins were not found on the file system: { rocks-git.nvim, foo.nvim }

[teto]

linked PR #35