Depot integration

[ibuildthecloud]

This is hack to leverage depot.dev for building. This will change in
the future and this is only a quick experiment.

Signed-off-by: Darren Shepherd darren@acorn.io

[cjellick]

Steps to use this:

1. Get a depot.dev account and proejct
2. Configure acorn to use an external registry by setting the install flag --internal-registry-prefix to your external registry of choice
3. Create a secret in your acorn proejct: acorn -j dev secret create depot-builder-key --data projectId=${PROJECT_ID},token=${TOKEN}