Add Docker Upload Action + build arm64 images

[cooperlees]

• Upload on every push to main for latest
• Also tag the release version when a new release is made
  • i.e. when you release a very the Git tag name is used for docker image tagging too - e.g. v1.1.1
• Also build a arm64/aarch64 build (e.g. for raspberry pi / apple M1)

This is in use for many project I contribute to.

Why do I want this?

• I'd like to run your frr_exporter on arm64/aarch64 boxes
  • On my raspberry pi in my RV is one example

What you'll need to do to use this

• Before merging add two secrets to you GitHub repo:
  • DOCKERHUB_USERNAME
  • DOCKERHUB_SECRET
  • This secret need to be a dockerhub secret you generate here: https://hub.docker.com/settings/security

How to add GitHub secrets: https://github.com/Azure/actions-workflow-samples/blob/master/assets/create-secrets-for-GitHub-workflows.md

Merge away and it should upload :)

[tynany]

Thanks for contributing!

Also build a arm64/aarch64 build (e.g. for raspberry pi / apple M1)

@cooperlees I don't see any changes that reflect the above. Is there a missing commit or file?