You can mount individual files. Below is from the docker documentation https://docs.docker.com/engine/userguide/containers/dockervolumes/
Mount a host file as a data volume
The -v flag can also be used to mount a single file - instead of just
directories - from the host machine.
$ docker run --rm -it -v ~/.bash_history:/root/.bash_history ubuntu /bin/bash
This will drop you into a bash shell in a new container, you will have
your bash history from the host and when you exit the container, the
host will have the history of the commands typed while in the
container.
Note: Many tools used to edit files including vi and sed --in-place may result in an inode change. Since Docker v1.1.0, this will produce an error such as “sed: cannot rename ./sedKdJ9Dy: Device
or resource busy”. In the case where you want to edit the mounted
file, it is often easiest to instead mount the parent directory.