While dependabot has turned out great to automate updating dependencies,
a major painpoint was that we had to manually run `make vendor` for each
and every commit. It was causing noise.
Adding the config file to `.github/dependabot.yml` will take of also
updating the `./vendor` tree. `containers/common` is using this config
for a while successfully.
[NO TESTS NEEDED]
Signed-off-by: Valentin Rothberg <rothberg@redhat.com>
