def-project-mode! :files does not work as documented

### What did you expect to happen?

When using def-project-mode! i expected that files starting with "." or ".." are treated as relative to buffer/default-directory as documented.
The macro is defined in core/autoload/projects.el.

### What actually happened?

Files are always treated as relative to project root (more specific doom-project-root)

### Describe your attempts to resolve the issue

Checked the implementation and it is based on project-file-exists-p!, that also claims to respect "." and ".." but is implemented as
`(file-exists-p! ,files (doom-project-root))`
and always treating files as project relative when inside a project.

### Steps to reproduce

Check output of e.g. `(project-file-exists-p! "../") from a buffer not directly in project root.

### System Information

https://pastebin.com/7rC05fjE