### Description

Recently, we added [a new DAG dependencies view](https://github.com/apache/airflow/pull/13199) to the webserver. It would be helpful if a similar diagram could also be displayed/generated using the CLI. For now, only [one DAG can be displayed](http://airflow.apache.org/docs/apache-airflow/stable/usage-cli.html#exporting-dag-structure-as-an-image) using CLI.
![image](https://user-images.githubusercontent.com/12058428/137945580-6a33f919-2648-4980-bd2c-b40cfcacc9fe.png)

If anyone is interested, I will be happy to help with the review.

### Use case/motivation

* Keep parity between CLI and web serwer.
* Enable the writing of scripts that use these diagrams, e.g. for attaching in the documentation.

### Related issues

https://github.com/apache/airflow/pull/13199/files

### Are you willing to submit a PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

tests/cli/commands/test_dag_command.py
mock_render_dag.return_value.pipe.return_value = b"DOT_DATA"
        mock_proc = mock.MagicMock()
        mock_proc.returncode = 0
        mock_proc.communicate.return_value = (b"OUT", b"ERR")
        mock_popen.return_value.__enter__.return_value = mock_proc
        with contextlib.redirect_stdout(io.StringIO()) as temp_stdout:
            dag_command.dag_show(
                self.parser.parse_args(['dags', 'show', 'example_bash_operator', '--imgcat'])
            )
        out = temp_stdout.getvalue()
        mock_render_dag.return_value.pipe.assert_called_once_with(format='png')
        mock_proc.communicate.assert_called_once_with(b'DOT_DATA')
        assert "OUT" in out
        assert "ERR" in out
    @mock.patch("airflow.cli.commands.dag_command.DAG.run")
    def test_cli_backfill_depends_on_past(self, mock_run):
        """
        Test that CLI respects -I argument
        We just check we call dag.run() right. The behaviour of that kwarg is
        tested in test_jobs
        """
        dag_id = 'test_dagrun_states_deadlock'
        run_date = DEFAULT_DATE + timedelta(days=1)
        args = [
            'dags',
            'backfill',
            dag_id,