Proposal: add support for "versions" property.

[wfouche]

In the future when versioning support is released, it would be very useful from a user perspective to be able to run a query to see what versions are available.

  "camel": {
      "script-ref": "./camel/${jbang.app.version:4.18.1}/CamelJBang.java",
      "versions": {
        "4.18.1": "Recommended stable version",
        "4.17.0": "Previous stable version",
        "4.9.0": "Legacy version"
      }
    }

A versions query command is not necessarily required. If you run a versioned alias command and the version is not valid, then as part of the exception message the availalbe versions could be displayed.