add home dir for spark user

[robbertvanwaveren]

It seems running basic commands inside the container like installing additional python packages with pip fails due to a lack of a home directory for the spark user. This PR solves that.

Not sure if that matches with the intended use-cases of the container but people are struggling with it.

related issues online: https://stackoverflow.com/questions/75560836/apach-spark-py-docker-image-error-could-not-install-packages-due-to-an-oserror https://stackoverflow.com/questions/2662598/grails-date-property-editor https://github.com/benniehaelen/delta-lake-up-and-running/issues/5