Use busybox in app container to enable easy copy

[r-n-o]

Convenience to enable init containers. I'm trying to write a kubernetes manifest which grabs the init binary from this image, and because there's no sh/utils I'd have to write a wrapper image to do this. Easy enough to include busybox here I think!

Here's what the init container looks like for the record:

initContainers:
  - name: pivot-extractor
    image: ghcr.io/anchorageoss/parser_app:$TAG@sha256:$SHA
    command: ["/bin/sh", "-c"]
    args:
      - cp /parser_app /pivot-binaries/visual_parser_app
    volumeMounts:
      - name: pivot-binaries
        mountPath: /pivot-binaries

How I tested this change

Newly built image works!

docker run -ti ghcr.io/anchorageoss/parser_app:latest@sha256:b9b21a09ebb6d9e4325e6c5e005305280afb8b990e4ab8cc1a636d974c34c382 -c "which cp"
/usr/bin/cp