Replace distutils copy_tree with shutil.copytree

[piotr1212]

distutils is removed from Python 3.12

fixes:

  File "/opt/hostedtoolcache/Python/3.12.0/x64/lib/python3.12/site-packages/mkdocs_monorepo_plugin/merger.py", line 16, in <module>
    from distutils.dir_util import copy_tree
ModuleNotFoundError: No module named 'distutils'

[baer95]

Hey @agentbellnorm is there any chance to get this reviewed and merged?

[agentbellnorm]

@piotr1212 Changes look good! Could you also update the changelog and setup.py? That way this will go out immediately without having to create a separate PR: https://github.com/backstage/mkdocs-monorepo-plugin#release

[hairmare]

this probably fixes #117

[bih]

Although this was created earlier, I see #118 also solves the problem. I'll merge that :)