Support the new Cloud Native Buildpack (CNB) format.

[feluxe]

Hi there,

we currently use heroku-buildpack-phoenix-static to deploy our phoenix app on kubernetes. This works because Heroku offers a converter-service (cnb-shim), which allows converting buildpacks from the old Heroku-Buildpacks format into the new Cloud-Native-Buildpacks format.

Unfortunately the converter seems to have some limitations, e.g. converted buildpacks don't seem to handle caching of layers properly, resulting in endless builds.

I was wondering if there are any plans to adopt the new CNB standard for heroku-buildpack-phoenix-static?