Create images for ARM

I'm using the ceph-exporter and noticed that only `linux/amd64` Docker images are available. I'd like to request that you also build and provide `linux/arm64` images alongside the existing ones. This would enable users, like myself, with ARM-based architectures to utilize the ceph-exporter without having to build their own images. Really appreciate the work you've put into this project! Thanks!

Start by locating the repository's existing Docker image build and publish configuration, then trace how the current linux/amd64 image is produced. Verify a linux/arm64 build alongside amd64 using the existing build process. Done means users can pull a published linux/arm64 ceph-exporter image without building it themselves.

Written by the indexing model from the issue text.