Add Kevin Alvarez (@crazy-max) as maintainer
Kevin is a maintainer for BuildKit, Buildx, and Docker's official GitHub
actions (among others), has been our "in-house GitHub actions expert"
for a long time, and has made significant contributions to the integration
with BuildKit, and to improve our build pipeline(s).
Kevin would be a great addition to our list of maintainers and to allow him
to perform his work in these areas in a more official capacity.
I nominated Kevin as maintainer, and votes passed, so opening a PR to
make it official.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>