### 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.
"""Parse comma-separated list and returns list of string (strips whitespace)."""
    return [x.strip() for x in val.split(",")]
def string_lower_type(val):
    """Lower arg."""
    if not val:
        return
    return val.strip().lower()
ARG_DAG_ID = Arg(("dag_id",), help="The id of the dag")
ARG_TASK_ID = Arg(("task_id",), help="The id of the task")
ARG_EXECUTION_DATE = Arg(("execution_date",), help="The execution date of the DAG", type=parsedate)
ARG_EXECUTION_DATE_OPTIONAL = Arg(
    ("execution_date",), nargs="?", help="The execution date of the DAG (optional)", type=parsedate
)
ARG_EXECUTION_DATE_OR_RUN_ID = Arg(
    ("execution_date_or_run_id",), help="The execution_date of the DAG or run_id of the DAGRun"
)
ARG_EXECUTION_DATE_OR_RUN_ID_OPTIONAL = Arg(
    ("execution_date_or_run_id",),
    nargs="?",
    help="The execution_date of the DAG or run_id of the DAGRun (optional)",
)
ARG_TASK_REGEX = Arg(("-t", "--task-regex"), help="The regex to filter specific task_ids (optional)")
ARG_SUBDIR = Arg(
    ("-S", "--subdir"),
    help=(
        "File location or directory from which to look for the dag. "
        "Defaults to '[AIRFLOW_HOME]/dags' where [AIRFLOW_HOME] is the "
        "value you set for 'AIRFLOW_HOME' config you set in 'airflow.cfg' "