[Issue 69] Updating Docker Image URL

[Rogibb111]

The current URL that I was supplying to the deploy_docker_image field for the Dokku GitHub Action was incorrectly formatted with upper case letters and also did not have the registry prepended. I am using the change-string-case-action to format the repository string correctly. I have also moved around environment variables and added the registry to the beginning of the URL. Changes in this PR include:

• Adding new workflow step with string case editor
• Moved the docker deploy job environment variables to the workflow level so they can be used in the Deploy App job
• Creating new docker image URL with the registry, lower case repo string, and the latest package version

Closes #69

[Rogibb111]

:tada: This PR is included in version 1.1.14 :tada:

The release is available on GitHub release

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