[dockerfile] vim is now the upstream project

[Honza Pokorny]

I am the original author and maintainer of the syntax files for
Dockerfiles. There was some confusion over the last few months as to
where the canonical upstream lies. There were three places where the
files lived:

* vim
* moby
* my original project

I have now reduced that number to one. I have archived my original
project[1]. I have submitted a PR to the moby project to remove those
files, and to add a note about the new upstream[2].

The vim project is now the canonical upstream. All patches should be
submitted here. I'll be reviewing old and stale PRs and patches
submitted in various places (GitHub, my inbox, etc). Feel free to
resubmit if you feel I have neglected your work. I'm happy if others
review patches; I don't intend to act like I'm in charge.

Thank you for your patience on this!

Honza

[1]: https://github.com/honza/dockerfile.vim/commit/b8c574928e503c0e94ad06647cff28b7c566af29
[2]: https://github.com/moby/moby/pull/40354