GitHub actions CI & CD

[adamus1red]

Adds support for builds using buildx on github actions.
This removes the need for seperate Dockerfiles for each platform and makes it easier to add or remove support for additional platoforms.

Currently this has a load of kitchen sink kind of builds which can be modified as required.

• Scheduled nightly build
• scheduled latest update every 2 weeks.
• branch named builds i.e. master
• short commit ID named builds i.e. sha-4104648
• release tag, unused but available.

Requires 3 secrets to be added to the repository for docker auth and image name.

• DOCKER_USERNAME
  • Username of user to push as i.e. dperson
• DOCKER_PASSWORD
  • Access token for the above username
• DOCKER_IMAGE
  • configurable image name e.g. dperson/torproxy

Note: To get the container to build it also includes #64 from @pubkey