perf: README.md add --rm to compose run web

[dhb52]

[MacLake]

This makes sense. You produce digital waste in form of a container that is created just for this command. With --rm this container will be deleted after the instruction has been carried out. Otherwise it is kept until you delete it e. g. with docker container prune.

[macolo]

thanks for this! I included this in #65 - closing this in favour of #65