### Body

The CLI:

`airflow variables set [-h] [-j] [-v] key VALUE`

https://airflow.apache.org/docs/apache-airflow/stable/cli-and-env-variables-ref.html#set_repeat1

Doesn't support adding description though column exists and we support it from Rest API:
https://airflow.apache.org/docs/apache-airflow/stable/stable-rest-api-ref.html#operation/post_variables

**The Task:**

Allow to set description from cli command

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.
except Exception as e:
            print(f"Variable import failed: {e!r}")
            fail_count += 1
        else:
            suc_count += 1
    print(f"{suc_count} of {len(var_json)} variables successfully updated.")
    if fail_count:
        print(f"{fail_count} variable(s) failed to be updated.")
    if skipped:
        print(
            f"The variables with these keys: {list(sorted(skipped))} "
            f"were skipped because they already exists"
        )
@providers_configuration_loaded
def variables_export(args):
    """Export all the variables to the file."""
    var_dict = {}
    with create_session() as session:
        qry = session.scalars(select(Variable))
        data = json.JSONDecoder()
        for var in qry:
            try:
                val = data.decode(var.val)
            except Exception:
                val = var.val
            var_dict[var.key] = val
    with args.file as varfile:
        json.dump(var_dict, varfile, sort_keys=True, indent=4)
        print_export_output("Variables", var_dict, varfile)