Version control for apt-get dependencies and LAMMPS

Currently, we do not version control our apt-get dependencies and LAMMPS. this is difficult to do, as we cannot do this through Dependabot.

Possible solutions:
- Move our apt-get dependencies to a file, and create a cron-based Github action that checks for new versions via a bash script, and creates pull requests as needed. You can read apt-get dependencies from a file, ignoring comments, with the line [`apt-get install $(grep -vE "^\s*#" filename | tr "\n" " ")`](https://askubuntu.com/questions/252734/apt-get-mass-install-packages-from-a-file).
- We could similarly use a file containing the LAMMPS version to version control LAMMPS, and pass the version into the Dockerfile as an environment variable.