Add MAP end-to-end testing GitHub Action

Either using the sample data in `/tests/data` or an entirely new test data subset, we need to implement an end-to-end GitHub Action in order to test the end-to-end process works.

e.g. GitHub Action should look in an `input` folder and produce an RT Struct file in an `output` folder.

Ideally this would be using the MAP container (see #24), but fallback would be to use `monai-deploy exec app -i input/ -o -output/` instead (assumption being that performance is expected to be the same as containerised MAP).

Start by reviewing the sample data in /tests/data and issue #24 for the MAP container approach. Inspect the repository's GitHub Actions setup and compare the container flow with `monai-deploy exec app -i input/ -o -output/`. Done means an end-to-end action processes input data and produces an RT Struct file in output.

Written by the indexing model from the issue text.