Provide some warning when docker mounts are empty because they're not mounted on the VM

### Description

I just spent a lot of time chasing down the issue described by [Issue with Docker bind mount showing empty](https://github.com/abiosoft/colima/blob/main/docs/FAQ.md#issue-with-docker-bind-mount-showing-empty) in the FAQ.

This behavior makes absolute logical sense once you realize it, but when you're working a couple layers of abstraction up the chain (in my case it was testing an AWS Lambda function locally, which worked when I did it directly in the terminal but failed when I tried to run it within vscode because that system quietly copies everything into `/tmp/aws-toolkit-vscode`, and that isn't mounted while `/Users/$USER` is), it's wildly non-obvious that "the application inside a container fails to find a file that I know exists" is caused by this issue, or what to even google for (I spent a while thinking it was maybe a docker issue or a macOS permissions problem before even looking at colima).

As a feature request, is there some way colima could provide a warning when a docker bind mount is empty because of this situation? I'm not sure if there's a logical way to surface this problem up the chain, but some kind of indication other than the mount just silently coming up empty would be a huge help to users.

Thanks for all your work!