Update the docker install docs

[kushalkolar]

Hi, I suggest updating the docker install docs, it didn't work for me without removing the slashes, I think readthedocs will wordwrap it anyways.

so:

docker run -it --shm-size=2G -v /path/to/user/data:/app/studio_data --env OPTINIST_DIR="/app/studio_data" --name optinist_container -d -p 8000:8000 --restart=unless-stopped oistncu/optinist:latest poetry run python main.py --host 0.0.0.0 --port 8000

Also might want to explain the shm-size parameter, if this is larger does it give more RAM to the container which would be necessary for processing larger movies?