protos: add chromiumdash milestone and fetch response

We'll be incorporating the release schedule into our configs and
one bit will be to request the schedule from the chromiumdash
and store it. This proto defines the reponses from the site.

BUG=chromium:1157948
TEST=./generate

Change-Id: I2af4a61a30889b34c3bc5407a5a5702b6258fd69
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/proto/+/2630927
Reviewed-by: Jack Neus <jackneus@google.com>
Reviewed-by: LaMont Jones <lamontjones@chromium.org>
Commit-Queue: George Engelbrecht <engeg@google.com>
2 files changed