### 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.
"Trigger a new DAG run. If DAG is paused then dagrun state will remain queued, "
            "and the task won't run."
        ),
        func=lazy_load_command("airflow.cli.commands.dag_command.dag_trigger"),
        args=(
            ARG_DAG_ID,
            ARG_SUBDIR,
            ARG_RUN_ID,
            ARG_CONF,
            ARG_EXEC_DATE,
            ARG_VERBOSE,
            ARG_REPLACE_MICRO,
            ARG_OUTPUT,
        ),
    ),
    ActionCommand(
        name="delete",
        help="Delete all DB records related to the specified DAG",
        func=lazy_load_command("airflow.cli.commands.dag_command.dag_delete"),
        args=(ARG_DAG_ID, ARG_YES, ARG_VERBOSE),
    ),
    ActionCommand(
        name="show",
        help="Displays DAG's tasks with their dependencies",
        description=(
            "The --imgcat option only works in iTerm.\n"
            "\n"
            "For more information, see: https://www.iterm2.com/documentation-images.html\n"
            "\n"
            "The --save option saves the result to the indicated file.\n"