(maint) Prevent inclusion of snk file
(maint) Prevent inclusion of snk file

While building the new Docker container, it was necessary to copy an
additional snk file into the root of the cloned repository. We don't
want this file to get committed into the repository, so lets make sure
to ignore it.

TheBigBear/choco,jberezanski/choco,jberezanski/choco,TheBigBear/choco,jberezanski/choco,TheBigBear/choco