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

[zachlipton]

Description

I just spent a lot of time chasing down the issue described by 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!