allow links to be followed in copy_media_files

[realjo]

I want to set up a small documentation server that checks out all our projects from a local
gitlab repo and link the docs directories of each of them as sub folders of a separate docs
folder with its own index.md file and a page for each project in the mkdoc.yml like in this example:

site_name: Our Documentation Collection
pages:
  - Home: index.md
  - project1: project1/index.md
  - project2: project2/index.md  

Because project1 and project2 are logical links to the git clone's docs directories, media files
are not copied to site_dir and thus e.g. images inside the projects not visible in the generated
html.

To fix it I propose to add ", followlinks=True" to os.walk in copy_media_files

def copy_media_files(from_dir, to_dir):
    """
    Recursively copy all files except markdown and HTML into another directory.
    """
    for (source_dir, dirnames, filenames) in os.walk(from_dir, followlinks=True):

[d0ugal]

Hmm, interesting. I wonder if this could cause any issues. I am not sure how I feel about this change, I will give it some thought. It does seem like quite a niche request given it hasn't been raised before.

[d0ugal]

I think I would be happy for this change to happen, I can't think of any problems with it and there have been no objections.