support for ARM64 build

[bohuslav-broza]

Hi,
we run Apache Pulsar on AWS Graviton instances (ARM64) and use this operator to manage Pulsar resources. However, the current docker image is only built for amd64, which prevents us from running it natively on our infrastructure.

Could you please add support for building and publishing an ARM64 image (or a multi-arch image)? This would help us run the operator without needing custom builds.

Thanks!