### 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.
GroupCommand(
        name="dags",
        help="Manage DAGs",
        subcommands=DAGS_COMMANDS,
    ),
    GroupCommand(
        name="tasks",
        help="Manage tasks",
        subcommands=TASKS_COMMANDS,
    ),
    GroupCommand(
        name="pools",
        help="Manage pools",
        subcommands=POOLS_COMMANDS,
    ),
    GroupCommand(
        name="variables",
        help="Manage variables",
        subcommands=VARIABLES_COMMANDS,
    ),
    GroupCommand(
        name="jobs",
        help="Manage jobs",
        subcommands=JOBS_COMMANDS,
    ),
    GroupCommand(
        name="db",
        help="Database operations",
        subcommands=DB_COMMANDS,
    ),