Document Docker usage

crates/bws/README.md

@@ -44,3 +44,45 @@ echo 'source <(/path/to/bws completions bash)' >> ~/.bashrc
 
 For more detailed documentation, please refer to the
 [Secrets Manager CLI help article](https://bitwarden.com/help/secrets-manager-cli/).
+
+### Docker
+
+You can also use the `bws` CLI with Docker:
+
+<!-- TODO: remove the build step once the Docker image is published to the Docker Hub -->
+
+```bash
+# From the root of the repository, build the Docker image:
+docker build -f crates/bws/Dockerfile --no-cache -t bitwarden/bws .
+
+# Run with Docker:
+docker run --rm -it bitwarden/bws --help
+```
+
+The Docker image is ran with a non-root user named `app`. If you need to pass your config file to
+the container, you can use the `-v`/`--volume` flag to mount your local `.bws` directory to the
+default location within the container:
+
+```bash
+docker run --rm -it -v "$HOME"/.bws:/home/app/.bws bitwarden/bws --help
+```
+
+Alternatively, you can use the `BWS_CONFIG_FILE` environment variable to specify the location of the
+config file within the container:
+
+```bash
+docker run --rm -it -e BWS_CONFIG_FILE="/path/to/config/file" -v /path/to/config/file:"$BWS_CONFIG_FILE" bitwarden/bws --help
+```
+
+Or, more concisely:
+
+```bash
+# Set the BWS_CONFIG_FILE environment variable on your host
+export BWS_CONFIG_FILE="/path/to/config/file"
+
+# Pass the BWS_CONFIG_FILE environment variable to the container
+docker run --rm -it -e BWS_CONFIG_FILE="$BWS_CONFIG_FILE" -v "$BWS_CONFIG_FILE":"$BWS_CONFIG_FILE" bitwarden/bws --help
+```
+
+Note that if you want to use identitcal config file paths on your host and in the container, the
+parent directory must exist on both.