Add support for other hardware platforms

# 💡 Summary #

Add support for other hardware platforms to this Docker image.

## Motivation and context ##

This will allow us to use AWS Graviton, for instance.

## Implementation notes ##

Note that this is not yet possible as there is not yet a multi-platform Docker image available for [cisagov/pshtt](https://github.com/cisagov/pshtt).

Review the Docker image build configuration and the upstream cisagov/pshtt image availability first. Confirm which hardware platforms must be supported, including AWS Graviton, and verify that a multi-platform pshtt image exists before defining the implementation. Done means the scanner image builds and runs on the agreed platforms.

Written by the indexing model from the issue text.