Add Puffin Docker image

[charliermarsh]

Missing piece for the release.

Test Plan

Built the image locally:

❯ docker run 99956098e1f8f04e209dcfc4a0afcee67df1fe8a726c164884e67f035b1a0f42
Usage: puffin [OPTIONS] <COMMAND>

Commands:
  pip    Resolve and install Python packages
  venv   Create a virtual environment
  clean  Clear the cache
  help   Print this message or the help of the given subcommand(s)

Options:
  -q, --quiet                  Do not print any output
  -v, --verbose                Use verbose output
  -n, --no-cache               Avoid reading from or writing to the cache
      --cache-dir <CACHE_DIR>  Path to the cache directory [env: PUFFIN_CACHE_DIR=]
  -h, --help                   Print help
  -V, --version                Print version