Requesting Chainguard nexus proxy

Feature description

Add the ability to install chainguard packages directly via apk from a wolfi base image

instead of manually pulling packages via the hardening_template - it'd be great to just use apk add <package> in Dockerfile

Makes adding core packages simpler and less error prone in an app image.

N/A

Chainguard apk index

Please read the Iron Bank Documentation for more info