Add workflow for end-to-end test (using Docker)

[hannahbast]

This workflow performs the following end-to-end test using the Docker setup:

1. Check out the code
2. Build a Docker image using the Dockerfile provided by the code
3. Download the PBF for Malta and built a TTL for it
4. Build a QLever index from the TTL, start a server, and query for the number of geometries