### 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.
("--ssl-key",),
    default=conf.get("webserver", "WEB_SERVER_SSL_KEY"),
    help="Path to the key to use with the SSL certificate",
)
ARG_WORKERS = Arg(
    ("-w", "--workers"),
    default=conf.get("webserver", "WORKERS"),
    type=int,
    help="Number of workers to run the webserver on",
)
ARG_WORKERCLASS = Arg(
    ("-k", "--workerclass"),
    default=conf.get("webserver", "WORKER_CLASS"),
    choices=["sync", "eventlet", "gevent", "tornado"],
    help="The worker class to use for Gunicorn",
)
ARG_WORKER_TIMEOUT = Arg(
    ("-t", "--worker-timeout"),
    default=conf.get("webserver", "WEB_SERVER_WORKER_TIMEOUT"),
    type=int,
    help="The timeout for waiting on webserver workers",
)
ARG_HOSTNAME = Arg(
    ("-H", "--hostname"),
    default=conf.get("webserver", "WEB_SERVER_HOST"),
    help="Set the hostname on which to run the web server",
)
ARG_DEBUG = Arg(
    ("-d", "--debug"), help="Use the server that ships with Flask in debug mode", action="store_true"
)