docs: update README

README.md

 # Ludwig Integration Test
 
-## Running integration test
+This repo contains the integration test for Ludwig.
+It is based on Selenium, which requires some additional packages to be available, therefore
+it is recommended to run the integration test inside of docker.
+It uses a docker bind volume to include the tests from the `tests` directory in the container.
+
+## Running the integration test
 
 ```bash
-docker compose run integration pytest
+export FE_VERSION=""    # container tag; defaults to latest
+export BE_VERSION=""    # container tag; defaults to latest
+docker compose run --rm integration pytest
 ```
+
+## Work in progress
+
+- Database migrations & data fixtures
+- Test isolation (wrt. data in the DB)