Github action to automate Docker image for SHACL API

[supermaxiste]

Dear Holger,

this PR includes a Github Action to automate the creation and sharing of the SHACL API Docker image. The Github action is triggered for every pull request and push to master and also for every release of the tool. This way the Docker image on Github will always be (automatically) up to date.

By accepting the PR, the current Dockerfile in the repository will not require updates every time there's a new release and docker users will have an easier time using the SHACL API Docker image. The PR uses Github Packages meaning that TopQuadrant can use its Github account and publish the Docker image on Github. This is an easier solution compared to creating a new account on DockerHub.

From your end we would ask you to do the following:

Enable public packages:

1. Go to organization page (github.com/TopQuadrant)
2. Settings
3. Packages
4. Tick the "Public" checkbox under "Package creation"

Give write permission to github actions:

1. Go to the repository page(github.com/TopQuadrant/shacl)
2. Settings
3. Actions > General
4. Under "Workflow permissions", set the radio menu to "Read and write permissions"

For any other questions or issues, don't hesitate to reach out.
On behalf of the SDSC-ORD,
Stefan

[HolgerKnublauch]

I don't have access to the TopQuadrant settings, but I have verified the shacl setting is already set. I can ask around if it doesn't work as you intend. Maybe the option is already set. I will merge the PR, maybe you can try it out?