Update README for Running with Docker

[nickevansuk]

The example in README.md is missing a mapping of the openactive-broker-microservice output folder (to ensure that validator output is accessible).

docker run -it \
  -e INPUT_CONFIG=/config/dev.json \
  -e NODE_ENV=dev \
  -p 3000:3000 \
  -v ${PWD}/config:/config \
  -v ${PWD}/packages/openactive-integration-tests/output:/openactive-test-suite/packages/openactive-integration-tests/output \
  ghcr.io/openactive/test-suite:latest \
  -- core

should be

docker run -it \
  -e INPUT_CONFIG=/config/dev.json \
  -e NODE_ENV=dev \
  -p 3000:3000 \
  -v ${PWD}/config:/config \
  -v ${PWD}/packages/openactive-integration-tests/output:/openactive-test-suite/packages/openactive-integration-tests/output \
  -v ${PWD}/packages/openactive-broker-microservice/output:/openactive-test-suite/packages/openactive-broker-microservice/output \
  ghcr.io/openactive/test-suite:latest \
  -- core

And other parts of the document that reference the mapping should also be updated.

This should be tested too.