Automatic merge from submit-queue

Add a multi-platform proposal

This is a proposal for the work I've done with multiarch Kubernetes. I've worked quite a lot on it and now I've written it down so others may easily use and learn from it, while at the same time pointing out issues that we should fix in the future.

I would like to get this in before `v1.3`.

Feel free to comment on it if it's something that's unclear.

@david-mcmahon @ixdy @mikedanese @Pensu @davidopp @bgrant0607 @dlorenc @eparis @vishh @thockin @dchen1107 @lavalamp