Publish scancode-toolkit Docker image to ghcr.io

## Short Description
Prepackage the software as a Docker image, hosted here on ghcr.io.

## Select Category
- [x] Packaging

## **Describe the Update**
Build and upload the Docker image to ghcr.io

## **How This Feature will help you/your organization**
It'll be much simpler to pull in without going through the build process.

## **Possible Solution/Implementation Details**
Perform the automation triggered in Github Actions upon release.

## **Can you help with this Feature**
#3027