Publish container into GHCR.io

[pperzyna]

Description

This PR adds workflow to GitHub Action that creates and publishes container image as an artefact to GitHub Container Registry. The build process is base on the best practices (includes opencontainers labels) and builds for two architecture: linux/amd64 and linux/arm64.

It produces:

• latest tag for the master branch
• X version tag according to SemVer
• X.Y version tag according to SemVer
• X.Y.Z version tag according to SemVer

Fixes #855

Unfortunately, The automatically generated GITHUB_TOKEN will not work for authentication for the initial release. It will require creating the ghcr.io/nccgroup/scoutsuite:latest manual for the first time.

Type of change

Select the relevant option(s):

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works (optional)
• [ ] New and existing unit tests pass locally with my changes