--static-dirs is resolved relative to working directory instead of slides source root

[kylrth]

If I run npx reveal-md /slides --static /static --static-dirs=assets when my current directory is /app, I get the following error:

[Error: ENOENT: no such file or directory, lstat '/app/assets'] {
  errno: -2,
  code: 'ENOENT',
  syscall: 'lstat',
  path: '/app/assets'
}

This even happens when I do --static-dirs=/slides/assets; the error complains that /app/slides/assets does not exist.